Cover Of Herbaceous Species Research Articles

Determinants of composition, diversity and structure in a seasonally dry forest in Myanmar

Seasonally dry forest with a deciduous canopy is a widespread ecosystem in Southeast Asia. Debate continues about whether this vegetation is forest or savanna. Savannas have tree cover <60%, C4-dominated ground vegetation, and frequent fires. Forests have tree cover >70%, C3-dominated ground vegetation, and infrequent fires. We studied three community types previously identified in seasonally dry forests in Myanmar, High Indaing, Low Indaing (both types of deciduous Dipterocarp-dominated forest) and Mixed Deciduous Forest (usually dominated by non-Dipterocarp species). We wanted to know whether their herbaceous layer communities were also compositionally distinctive, whether their structure (% tree cover, C4 abundance) identified them as savannas or forests, and whether they differed with respect to soil nutrients, and fire frequency.We sampled fifteen 50 m × 50 m plots thought to represent the 3 community types (5 plots of each community type). In each plot we measured basal area, abundance and richness of trees with DBH ≥5 cm, and percentage cover, abundance and richness of herbaceous layer species, and classified each species as C3/C4. We estimated tree cover along four 50 m line transects recording canopy openness/closure every 1 m. We pooled six 0–15 cm soil cores to estimate soil parameters (N, P, K, pH). We recorded fire frequency in each plot using MODIS fire products for 2001–2017.We found that tree, herbaceous-layer and combined compositional data generated similar community clusters. Low Indaing had open tree canopies and high abundance of C4 plants relative to Mixed Deciduous Forest. High Indaing had a wider range of tree covers but also high C4 abundance. Fire was common in all three communities. Low Indaing could be differentiated from Mixed Deciduous forest by soil K and P (lower for Low Indaing), with High Indaing having intermediate values.Low Indaing appears to be a type of savanna whereas Mixed Deciduous Forest is a type of forest, but with the propensity to burn. In our data, High Indaing showed characteristics of both savanna and forest. Although soils underlie the transitions between these Asian communities, they do not show the clear physiognomic boundaries observed in African and South American savanna-forest transitions.

Short-duration rotational grazing leads to improvements in landscape functionality and increased perennial herbaceous plant cover

Livestock grazing can lead to reduced ground cover and altered composition of pastures through the loss of palatable forage species and reduced litter cover. This negatively impacts landscape function and ultimately livestock production. Grazing livestock for short periods with high animal density, followed by long rests to allow pasture recovery (short-duration grazing), could be a way to address these issues. In naturalised pastures, we assessed landscape functioning and compared the abundance of six major plant functional groups at 36 sites on 12 commercial grazing properties. Six of the properties had been managed with short-duration grazing for more than 7 years (in most cases over 10 years), while the six control properties were managed with grazing that was more typical of the region (relatively continuous throughout the year with unplanned rests). Under short-duration grazing, there was approximately 19% greater foliar cover of perennial herbaceous species with a corresponding 14% reduction in foliar cover of introduced annual plants. Attributes relating to biophysical functioning of the landscape were enhanced by short-duration grazing, with environmental factors less important in influencing these landscape function attributes. Higher-value forage species were also more abundant on short-duration grazing properties, especially at higher rainfall sites. Conversely, species that tend to increase under heavy grazing pressures, and are of lower forage value, were less abundant under short-duration grazing. Despite the changes in pasture composition in response to grazing management there was a large amount of unexplained variation in herbaceous community composition. This study demonstrates benefits for landscape function and naturalised pasture composition under short-duration grazing that has been in place for several years compared with more usual grazing practices.

Drought in Southern California coastal sage scrub reduces herbaceous biomass of exotic species more than native species, but exotic growth recovers quickly when drought ends

Semi-arid regions with Mediterranean-type climates harbor exceptional biodiversity, but are increasingly threatened by invading exotic annual species and climatic changes, including drought. In semi-arid ecosystems, antecedent conditions often influence plant growth, but the role of antecedent conditions for drought response and recovery of native versus exotic species remains largely unexplored. From 2013 to 2016, we imposed experimental rainfall treatments (average rainfall, moderate or severe drought) in plots under a native shrub canopy and in inter-spaces dominated by herbaceous vegetation, and quantified growth (peak biomass) and abundance (cover) of native and exotic herbaceous species. The following year, we quantified recovery from the drought treatments (2017). Exotic biomass was less resistant to drought (declined more than native biomass), but was more resilient (increased more than native biomass in the year following drought), especially in unshaded inter-spaces between shrubs. These responses were associated with life history; annual species responded more negatively to drought in the inter-spaces than perennial species. Current years' rainfall was a better predictor of biomass than prior rainfall, but antecedent factors were also important. After four years of rainfall treatments, exotic species had the highest growth recovery in the severe drought treatment, while growth of natives had the opposite response. In contrast, litter was positively associated with plant growth regardless of origin. This study demonstrates that when native and exotic species differ in life history, as they do in Mediterranean climate ecosystems, they may respond differently to antecedent factors, and hence differ in recovery from climate extremes such as drought.

Alternative pathways to landscape transformation: invasive grasses, burn severity and fire frequency in arid ecosystems

Summary Arid ecosystems are often vulnerable to transformation to invasive‐dominated states following fire, but data on persistence of these states are sparse. The grass/fire cycle is a feedback process between invasive annual grasses and fire frequency that often leads to the formation of alternative vegetation states dominated by the invasive grasses. However, other components of fire regimes, such as burn severity, also have the potential to produce long‐term vegetation transformations. Our goal was to evaluate the influence of both fire frequency and burn severity on the transformation of woody‐dominated communities to communities dominated by invasive grasses in major elevation zones of the Mojave Desert of western North America. We used a chronosequence design to collect data on herbaceous and woody cover at 229 unburned reference plots and 578 plots that burned between 1972 and 2010. We stratified the plots by elevation zone (low, mid, high), fire frequency (1–3 times) and years post‐fire (YPF; 1–5, 6–10, 11–20 and 21–40 YPF). Burn severity for each plot was estimated by the difference normalized burn ratio. We identified two broad post‐fire successional pathways. One was an outcome of fire frequency, resulting in a strong potential transformation via the grass/fire cycle. The second pathway was driven by burn severity, the critical aspect being that long‐term transformation of a community could occur from just one fire in areas that burned at high or sometimes moderate severity. Dominance by invasive grasses was most likely to occur in low‐and high‐elevation communities; cover of native herbaceous species was often greater than that of invasive grasses in the mid‐elevation zone. Synthesis. Invasive grasses can dominate a site that burned only one time in many decades at high severity, or a site that burned at low severity but multiple times in the same time period. However, high burn severity may predispose areas to more frequent fire because they have relatively high cover of invasive annual grass, suggesting burn severity and fire frequency have both independent and synergistic effects. Resilience in vegetation structure following fire in many arid communities may be limited to a narrow window of low burn severity in areas that have not burned in many decades.

Effects of conifer treatments on soil nutrient availability and plant composition in sagebrush steppe

Piñon-juniper woodlands of the western United States have expanded 2 to 10-fold since the late 1800’s. Tree control measures using chainsaws, heavy equipment and prescribed fire have been used to reduce woodlands and restore big sagebrush steppe and decrease woody fuel loading. We evaluated nutrient availability and herbaceous recovery following various cutting and prescribed fire treatments in late succession western juniper woodlands on two sites in southeast Oregon from 2007 to 2012. Sites were a cool, wet big sagebrush-Idaho fescue association (FESCUE), highly resistant to exotic annual grasses and a warm dry big sagebrush-bluebunch wheatgrass association (BLUEBUNCH), moderately resistant to annual grass invasion. Treatments were untreated controls, partial cutting followed by fall broadcast burning (SEP), cut and leave (CUT), and cut and burn in winter (JAN) and spring (APR). Soil inorganic N (NO3−, NH4+), phosphorus (H2PO4−), potassium (K+), and cover of herbaceous species were measured in three zones; interspace, litter mats around the tree canopy (canopy), and beneath felled trees (debris). Following woodland cutting, the results of the various slash treatments measured significant differences through time in the availability of inorganic N, P, and K and vegetation composition. Peak nutrient availability tended to occur within the first two years after treatment. The increases in N, P, and K were greatest in severely burned debris and canopy zones of the SEP and APR treatments. Invasive annual grass cover was positively correlated to soil inorganic N concentrations. Herbaceous composition at the FESCUE site was generally resistant to annual grasses after juniper treatments and native plants dominating post-treatment even in highly impacted debris and canopy zones of the SEP treatment. The BLUEBUNCH site was less resistance and resilient, thus, exotic annual grasses were a major component of the understory especially when tree and slash burning was of high fire severity. To lessen these impacts requires slash burning be applied from late fall to early spring, when fuel moisture and relative humidity are higher, to maintain an adequate perennial herbaceous composition for recovery.

Vegetation Changes in a Native Forest Produced by Atta vollenweideri Forel 1893 (Hymenoptera: Formicidae) Nests.

Herbivory is an important factor to generate spatial mosaics with variations in a plant community composition and organization. The objective of this work was to determine the impact of Atta vollenweideri Forel 1893 nests on herbaceous and shrub vegetation in a degraded native forest of the Espinal ecoregion. The study was carried out in the Protected Area and Multiple Use Nature Reserve called Estancia "El Carayá" (Entre Ríos, Argentina). Ten A. vollenweideri nests were selected by simple random sampling through internal roads, and two transects were drawn from the center of the nest (0m) up to 60m away in opposite directions. The line intercept method was used to quantify the percentage of vegetation cover of herbaceous and shrub species, while the floristic composition was estimated by the Canfield method. Afterwards, a nonparametric test between positions and a conglomerate analysis to evaluated distance were applied. Grass species, legumes, and sedges fell in the adjacent areas to nests, highlighting the bare soil at the crest and base of the nests. Fifteen plant species were identified, and two families correspond to monocotyledonous and dicotyledonous species. In conclusion, the nests of A. vollenweideri affect the community of herbaceous and shrub vegetation of the studied degraded native forest of the Espinal ecoregion since these ants perform a high selection of herbaceous species considered as pioneers of plant successions.

Interactive effects of land-use history, tree encroachment and distance to edge on species richness in an unmanaged heathland

Questions How do land-use legacies, tree encroachment and distance to the edge interact to determine species richness patterns in the ground vegetation of an unmanaged heathland? What are the direct and indirect effects of these factors? Do different functional groups respond differently to these factors? Location Norholm heathland, southwest Denmark. Methods We recorded the overstorey and ground vegetation along with environmental variables in 129 plots on a 350 ha heathland where management ceased more than 100 yrs ago. We used structural equation models (SEM) to examine the relationship between species richness of functional groups (herbs, dwarf shrubs and tree seedlings) and ground vegetation cover, overstorey development, distance to the edge and nutrient availability. Results The relative importance of the driving factors differed between functional groups. Herb richness increased with increasing nutrient availability from previous land use and decreased with overstorey development. Dwarf shrub richness responded negatively to overstorey development and herb cover. In contrast, species richness of tree seedlings responded strongly and positively to overstorey development but not to environmental variables or ground vegetation. In general, the effect of nutrient availability and distance to the edge were of similar magnitude and were largely mediated by the overstorey and ground vegetation. Conclusions Land-use legacies and tree encroachment can have differential effects on the species richness of different functional groups. Typical heathland dwarf shrubs were able to withstand moderate levels of increased nutrient availability and tree colonization. However, the combination of these factors poses a serious threat, as dwarf shrub richness decreased due to an increase in the cover of herbaceous species and light limitation. The absence of management did not lead to a rapid loss of typical heathland species.

Hydrologic restoration in a dynamic subtropical mangrove‐to‐marsh ecotone

AbstractExtensive hydrologic modifications in coastal regions across the world have occurred to support infrastructure development, altering the function of many coastal wetlands. Wetland restoration success is dependent on the existence of hydrologic regimes that support development of appropriate soils and the growth and persistence of wetland vegetation. In Florida, United States, the Comprehensive Everglades Restoration Program (CERP) seeks to restore, protect, and preserve water resources of the greater Everglades region. Herein we describe vegetation dynamics in a mangrove‐to‐marsh ecotone within the impact area of a CERP hydrologic restoration project currently under development. Vegetation communities are also described for a similar area outside the project area. We found that vegetation shifts within the impact area occurred over a 7‐year period; cover of herbaceous species varied by location, and an 88% increase in the total number of mangrove seedlings was documented. We attribute these shifts to the existing modified hydrologic regime, which is characterized by a low volume of freshwater sheet flow compared with historical conditions (i.e. before modification), as well as increased tidal influence. We also identified a significant trend of decreasing soil surface elevation at the impact area. The CERP restoration project is designed to increase freshwater sheet flow to the impact area. Information from our study characterizing existing vegetation dynamics prior to implementation of the restoration project is required to allow documentation of long‐term project effects on plant community composition and structure within a framework of background variation, thereby allowing assessment of the project's success in restoring critical ecosystem functions.

English

Diversity of woody and herbaceous species, stand structure and regeneration status of woody species, spatial cover of the herbaceous species as well as nutritional values of woody and herbaceous species were studied in Mokolodi Nature Reserve (MNR), Botswana. Ten 1 ha quadrats were used to collect data, and in each quadrat, ten 1 m2 plots were used to estimate the spatial cover of herbaceous species. MNR exhibited high species, genera and family richness, but low diversity and eveness. The diversity and eveness values of woody species were 1.44 and 0.38, respectively. Density of woody species was about 4,785 ha-1. Most of the woody species demonstrated unstable population structures and hampered natural regeneration. The spatial cover of all herbaceous species was only 44.67% ha-1. The nutritional values of the species ranged between low and high while there was no information on the nutrtion values for 16 and 55% of the woody species and herbaceous species, respectively. The dominance values of woody species indicate inadequate number of big-sized trees, and that MNR is still at the recovery phase. For 68% of the woody species, natural regeneration is hampered. Future research topics and recommendations on the future management of MNR are proposed. Key words: Density, dominance, evenness, frequency, importance value index, nutritional value, over grazing, population structure, soil erosion, species richness.

Variation In Old-Growth Coast Redwood (Sequoia sempervirens) Reference Sites In Mendocino County, California

Abstract Restoration and management of old-growth conditions in coast redwood (Sequoia sempervirens [D. Don] Endl.) forests are traditionally based on an idealized set of characteristics that occur in productive stands. We compared three old-growth sites to quantify variability among remaining reference stands of the central coast redwood range in Mendocino County, California. Two of the sites are protected from coastal influence, have rich alluvial soils, and relatively high visitor usage. The third site is in close proximity to the coast with variable soil conditions and little visitor access. We randomly sampled twenty, 20-meter circular diameter plots in each site to evaluate basal area, tree density, species richness, canopy cover, shrub cover, and herbaceous species cover. We conducted multivariate analyses including nonmetric multidimensional scaling (NMDS), perMANOVA, and indicator species analysis (ISA) to examine the structural clustering and compositional metrics among the sites. Results indica...

Лесоводственная оценка сосновых насаждений в зоне рекреационного воздействия в Воронежской области

The paper presents a silvicultural assessment of the status and sustainability of the compo-nents of phytocenosis in pine plantations, analysis of the state density of the soil depending on the intensity of recreational activity. With increasing stage of recreational digression was clearly manifested by the reduction of biophysical parameters (diameter, height, completeness, margin). With increasing recreational pressure reduced the species diversity of underwood species, pro-jective cover of herbaceous plants, forest disappear (Lily of the valley, wild strawberry and mea-dow appear) and weed species.

Shrub encroachment influences herbaceous communities in flooded grasslands of a neotropical savanna wetland

AbstractQuestionThe encroachment of woody species has been globally reported over much of arid and semi‐arid biomes, and has been associated with a decrease in cover and number of herbaceous species. How does the encroachment of a woody shrub affect herbaceous community structure and species composition in grasslands of a wetland ecosystem?LocationSeasonally flooded grasslands in a Neotropical Hyperseasonal Savanna, the Pantanal wetland, Brazil.MethodsWe investigated the effect of the encroaching plant Combretum laxum on a herbaceous community from seasonally flooded grasslands in the Pantanal wetland using 29 vegetation samples representing encroachment at different spatio‐temporal stages. The point quadrat method was used to acquire vegetation data, as plant cover, species richness (S) and Shannon‐Wiener diversity index (H’). We evaluated the existence of stages of encroachment related to differences in vegetation structure and species composition using non‐metric multidimensional scaling ordination and analysis of similarity. The response of the herbaceous community to shrub advance was analysed using linear and quadratic polynomial regression models. Model fitness was tested using the ACI.ResultsThe advance of the woody encroaching plant C. laxum over the seasonally flooded grassland occurs in three stages: grassland stage, shrub islands stage and shrubland stage. The initial advance of C. laxum over the grassland, represented by the shrub islands stage was correlated to an increase in species richness and a decrease in important native forage grasses. Critical changes in the herbaceous community were observed when the encroaching plant covered &gt;30% of the periodically flooded grassland, when the richness of herbaceous species dropped from 22 to four.ConclusionsWoody encroachment causes impoverishment and simplification of the herbaceous community. The shift from a grass‐ to a shrub‐dominated state is related to the reduction in important grassland‐obligate species, forage resources for herbivore livestock and wild animals, affecting the ecological dynamics and the economy of rangelands. Conservation of these grassland ecosystems depends on rangeland management practices guided by scientific knowledge on the causes and consequences of plant community changes.

Identifying key climate and environmental factors affecting rates of post-fire big sagebrush (Artemisia tridentata) recovery in the northern Columbia Basin, USA

Sagebrush steppe of North America is considered highly imperilled, in part owing to increased fire frequency. Sagebrush ecosystems support numerous species, and it is important to understand those factors that affect rates of post-fire sagebrush recovery. We explored recovery of Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) and basin big sagebrush (A. tridentata ssp. tridentata) communities following fire in the northern Columbia Basin (Washington, USA). We sampled plots across 16 fires that burned in big sagebrush communities from 5 to 28 years ago, and also sampled nearby unburned locations. Mixed-effects models demonstrated that density of large–mature big sagebrush plants and percentage cover of big sagebrush were higher with time since fire and in plots with more precipitation during the winter immediately following fire, but were lower when precipitation the next winter was higher than average, especially on soils with higher available water supply, and with greater post-fire mortality of mature big sagebrush plants. Bunchgrass cover 5 to 28 years after fire was predicted to be lower with higher cover of both shrubs and non-native herbaceous species, and only slightly higher with time. Post-fire recovery of big sagebrush in the northern Columbia Basin is a slow process that may require several decades on average, but faster recovery rates may occur under specific site and climate conditions.

Herbaceous Flora of Sacred Grooves in Perumudiyoor, Muthuthala Gramapanchayath, Pattambi

The herbaceous flora of sacred groves of Perumudiyoor region has analysed taxonomically and phytosociologically. There are 165 angiosperms, 1 Gymnosperm and 2 Pteridophytes belongs to 62 families. The herbaceous flora consists of 43 species in 22 families. The dominant families of herbaceous members are Amaranthaceae and Asteraceae. The vegetation profile of the sacred groves in Perumudiyoor consists of 43 herbs, 24 shrubs, 9 climbers, 1 epiphyte and 59 trees. The most frequent herbs are Commelina diffusa , and Ruellia prostrata . Curculigo orchioides has highest density and highest abundance which contribute the highest percent in the ground cover of herbaceous species. The Shannon Weiner diversity Index (H') is 1.80695667 which indicates the species are distributed uniformly and shows high diversity without dominant species.

Seasonal burning of juniper woodlands and spatial recovery of herbaceous vegetation

Decreased fire activity has been recognized as a main cause of expansion and infilling of North American woodlands. Piñon-juniper (Pinus-Juniperus) woodlands in the western United States have expanded in area 2–10-fold since the late 1800s. Woodland control measures using chainsaws, heavy equipment and prescribed fire are used to restore big sagebrush (Artemisia tridentata Nutt.) steppe plant communities and reduce woody fuel loading. Immediate objectives in the initial control of piñon-juniper are; (1) recovery of perennial herbaceous species to restore site composition, structure and processes (resilience) and resist invasion and dominance by invasive annual grasses (resistance) and (2) reducing woody fuel accumulations. Spanning a 7year period (2006–2012), we compared herbaceous recovery following cutting and prescribed fire on three sites in mid and late succession western juniper (Juniperus occidentalis spp. occidentalis Hook.) woodlands in southeast Oregon. Treatments were untreated controls, partial cutting followed by fall broadcast burning (SEP), clear-cut and leave (CUT), and clear-cut and burn in winter (JAN), and spring (APR). Cover of herbaceous species was measured in three zones; interspace, litter mats around tree stumps (stump), and beneath felled trees. In interspace zones of all treatments, comprising between 51% and 63% of site areas, perennial bunchgrasses dominated two sites and co-dominated with invasive annual grasses at one site after treatment. Burning in the JAN treatments, when fuel moisture and relative humidity were high and temperatures cooler, reduced disturbance severity in stump and felled tree zones, which maintained perennial herbaceous understories and prevented or limited the presence of invasive annuals. Burning felled juniper in SEP and APR treatments resulted in moderate to high fire severity in stump and felled tree zones. At two sites, these fires consumed all fuel up to the 1000-h fuel class, largely eliminated herbaceous perennials, and created islands within treatments that enhanced annual grass invasion and dominance. To maintain or boost site resilience and resistance following control of late successional woodlands, reducing piñon-juniper fuels by burning in winter provides managers with a low-impact option for conserving sagebrush steppe.

Urban Park Soil and Vegetation: Effects of Natural and Anthropogenic Factors

Various soil surface components, such as trees, shrubs and biological crusts, and human recreational activities, e.g., barbecues and trampling by visitors, may divide the area of the urban park into smaller fragments/microenvironments, differentiated by their microenvironmental conditions, which may differ in soil and vegetation characteristics. The spatial changes in the soil and vegetation characteristics and their causes were investigated in an urban park located south of Tel Aviv-Jaffa, Israel. The area of the park is 0.5 km2 including groves, a lake, lawns, and rest areas. Soil was sampled in nine microenvironments, of which seven were within the park: under Ceratonia siliqua trees (CsU), under Ficus sycomorus trees (FiU), rest area between tables under F. sycomorus (FiB), rest area under tables under F. sycomorus (FiT), open area with bare soil (OaS), open area with biological crust cover (OaC), and open area covered by herbaceous vegetation (OaV). Two more microenvironments, planar and sloping open areas (CoP and CoS, respectively) in the vicinity of the park, were used as the controls. Electrical conductivity, concentrations of soluble ions (Mg2+, Ca2+, Na+, K+ and HCO−3), pH, contents of organic carbon, calcium carbonate and moisture, and grain size distribution were determined. In addition, herbaceous vegetation cover, number and diversity of herbaceous vegetation species were measured. It was found that soil properties and herbaceous vegetation characteristics varied within the park. Soil organic carbon, electrical conductivity, soluble salts, penetration depth, and vegetation characteristics were affected by human activities, mainly in the rest area between the tables. In contrast, the above characteristics were affected by natural factors mainly in the rest of the microenvironments, which were subjected to low levels of anthropogenic intervention. The heterogeneous structure of the park, as represented by the various microenvironments, offered new habitats and promoted the preservation of natural vegetation.

Post-dispersal predation of Pinus pinaster Aiton seeds: key factors and effects on belowground seed bank

Seed bank dynamics constitute a pool of natural regeneration, a complex and key process for stand persistence. The present work analyzes post-dispersal predation on a Pinus pinaster Ait. (maritime pine) belowground seed bank. The study was carried out at the experimental site of Mata de Cuellar (Segovia, central Spain), where an integrated analysis of maritime pine regeneration has been underway since 2004. Seed predation was monitored every month from 2010 to 2013. A generalized linear model was fitted using “next spring seed density” as the response variable and seed rain, micro-site conditions and annual climate variability as explanatory variables. Seed rain, distance to the nearest stump, basal area and Walter’s drought index, along with percentage cover of herbaceous species, pine needle litter and shrub species, had significant positive effects. The number of neighboring trees had a significant negative effect on seed density. These results demonstrate how seed rain, summer drought and micro-site conditions are crucial to understand the effects of predation on the belowground seed bank. Though greater than null, the final seed bank might be insufficient for successful natural regeneration due to high mortality caused by difficult germination and establishment conditions.

Soil Resources Influence Vegetation and Response to Fire and Fire-Surrogate Treatments in Sagebrush-Steppe Ecosystems

Current paradigm suggests that spatial and temporal competition for resources limit an exotic invader, cheatgrass (Bromus tectorum L.), which once established, alters fire regimes and can result in annual grass dominance in sagebrush steppe. Prescribed fire and fire surrogate treatments (mowing, tebuthiuron, and imazapic) are used to reduce woody fuels and increase resistance to exotic annuals, but may alter resource availability and inadvertently favor invasive species. We used four study sites within the Sagebrush Steppe Treatment Evaluation Project (SageSTEP) to evaluate 1) how vegetation and soil resources were affected by treatment, and 2) how soil resources influenced native herbaceous perennial and exotic annual grass cover before and following treatment. Treatments increased resin exchangeable NH4+, NO3-, H2PO4-, and K+, with the largest increases caused by prescribed fire and prolonged by application of imazapic. Burning with imazapic application also increased the number of wet growing degree days. Tebuthiuron and imazapic reduced exotic annual grass cover, but imazapic also reduced herbaceous perennial cover when used with prescribed fire. Native perennial herbaceous species cover was higher where mean annual precipitation and soil water resources were relatively high. Exotic annual grass cover was higher where resin exchangeable H2PO4- was high and gaps between perennial plants were large. Prescribed fire, mowing, and tebuthiuron were successful at increasing perennial herbaceous cover, but the results were often ephemeral and inconsistent among sites. Locations with sandy soil, low mean annual precipitation, or low soil water holding capacity were more likely to experience increased exotic annual grass cover after treatment, and treatments that result in slow release of resources are needed on these sites. This is one of few studies that correlate abiotic variables to native and exotic species cover across a broad geographic setting, and that demonstrates how soil resources potentially influence the outcome of management treatments.

Factors influencing natural regeneration of totara (Podocarpus totara D.Don) on grazed hill country grassland in Northland, New Zealand

There is increasing interest in establishing indigenous forests on marginal pastoral hill country in New Zealand to improve soil conservation, water quality and indigenous biodiversity. Large-scale reforestation using native seedlings is extremely costly. However, given suitable seed sources, it is possible to encourage natural regeneration of grassland into native plants. A grazed, sloping pasture site in Northland where totara (Podocarpus totara D.Don) regeneration had been allowed to develop over a 10-year period was assessed using a grid of 2-metre diameter plots. Counts of regenerating woody species and cover of herbaceous species were obtained in each plot. Plots were classified on the basis of herbaceous species cover using the TWINSPAN classification procedure. Regression analyses were used to identify site factors and characteristics of the herbaceous vegetation associated with totara regeneration. More than 7,000 stems ha−1 of woody species, mostly totara and gorse (Ulex europaeus L.), had accumulated over the 10-year period despite the presence of cattle grazing. Regeneration of totara was associated with steeper slopes and sites with the greatest diversity of herbaceous species but with lower overall levels of herbaceous cover. The regeneration pattern of the other main woody species was similar although gorse colonised a wider range of sites. Regeneration of woody species was absent on flatter sites, which were dominated by a few high-fertility tolerant herbaceous species and had high levels of herbaceous cover. This study has shown that regeneration of totara on a pastoral hill-country site was most prevalent on steeper slopes of lower fertility with typically sparse vegetation cover comprising low fertility tolerant herbaceous species. Conversely, totara regeneration was absent on flatter areas of higher fertility. It seems likely that grazing assists totara regeneration by keeping pasture cover short, thus increasing light levels near ground level for newly germinated seedlings. The propensity for totara to regenerate on pastoral hill country in the presence of grazing and where there is a nearby seed source could provide a practical option for re-establishing indigenous woody vegetation on erosion-prone marginal land.

Plant-community responses to shrub cover in apáramograssland released from grazing and burning

Shrub encroachment can follow grazing or burning release in páramo grasslands. While encroachment decreases herbaceous species richness in some grassland systems, the effects of this process on the herbaceous community in páramo grasslands are currently unknown. We collected data on shrub cover, herbaceous-species cover and species composition in a páramo grassland 12 years after release from burning and cattle grazing near Zuleta, Ecuador. Topographic and soil measures were also included as predictor variables of differences in community composition. Contrary to studies in other systems, shrub cover did not have a significant effect on herbaceous-species richness, whereas shrub-species richness significantly increased with shrub cover. However, shrub cover was associated with significant shifts in herbaceous–community composition. Most notably, there was an increase in some shade-tolerant forbs and tall-statured wetland grasses with increasing shrub cover, and a corresponding decrease in some short-statured grasses and early successional forbs. These results could indicate that the ameliorative effects of shrubs (e.g. frost and wind protection) in harsh alpine environments may partially compensate for the expected competitive effect of shrubs due to shading.