Shrub Component Research Articles

Structural Differences in Herbaceous Communities on Edge and Interior Atlantic Forest in South Brazil

The Atlantic Forest is recognized worldwide as hotspots due to its megadiversity. This study aimed to evaluate whether there are differences between the floristic and structural diversity of the herbaceous component in an edge and interior region of the southern Brazilian Atlantic Forest. The study was developed in a forest fragment located in the state of Santa Catarina, south Brazil. The edge of the fragment is characterized by an area up to 10-15m wide, covered massively by herbaceous-subshrub vegetation and rare arboreal individuals. The interior is discontinuously shaded by the arboreal and shrub component contained in the upper strata of the forest. The phytosociological survey used the plot method. 100 plots of 1 m² were established, 50 on the edge of the forest fragment and 50 plots inside it. The phytosociological parameters studied for both areas were absolute frequency (AF), relative frequency (RF), absolute coverage (AC) and relative coverage (RC). Through the treatment and analysis of these data, the importance value index (IVI) of each species was obtained. At the edge of the forest fragment, 18 families and 34 species were identified. Of the 34 species found, 31 are angiosperms (24 dicots and 7 monocots) and 3 are monilophytes. All species are native to the Brazilian flora, with the exception of Centella asiatica and 2 lycophytes. In the interior, 14 species were found, being represented by 10 families. All species in the interior were angiosperms (4 dicots and 8 monocots) and 2 monilophytes. All species are native to the Brazilian flora and have herbaceous habit. The herbaceous community in the interior is different from the herbaceous community at the forest edge. The initial hypothesis of the work was confirmed, since none of the species present at the edge of the forest occurs in the interior of the forest.

Floristic and phytosociological analysis of the tree and shrub component of Clementino Procópio square, Campina Grande, PB

Squares are of great importance for the sociability of a population and the configuration of a city. This research aimed to carry out a qualitative and quantitative analysis of the tree and shrub components of Clementino Procópio square in the city of Campina Grande (PB). Specimen data collection was carried out through a census and analysis was carried out using phytosociological parameters and multivariate analysis. It was found that exotic species are more predominant. Fabaceae, Arecaceae and Bignoniaceae were the families with the highest number of species. The species F. retusa and H. heptaphyllus had more number of specimens, more density and dominance, more importance and coverage. The tree density indices, Shannon-Winer and Pielou, showed that the square has enough number of trees, high species diversity and high equitability.

Flora and similarities of a rocky outcrop in the Caatinga, eastern region of South America

Rocky environments show great habitat heterogeneity and very specific microclimatic characteristics that select for appropriately adapted floristic assemblages. A floristic survey was carried out on a rock outcrop in the driest portion of the Cariri Environmental Protection Area (APA) in Paraíba State, northeastern Brazil, to determine its similarity to other Caatinga sites. We recorded 128 species distributed among 103 genera and 52 families. Fabaceae, Convolvulaceae, Malvaceae, Euphorbiaceae, Asteraceae, Cactaceae, Bromeliaceae, Rubiaceae, and Poaceae were the most representative families in terms of numbers of species, with a high representation of herbaceous and shrub components and a predominance of typically Neotropical species, in addition to endemic taxa. Pectis linifolia L. (Asteraceae) is recorded here for the first time in the Paraíba state, Brazil. Similarity analysis evidenced that the study area, located in an extremely dry Caatinga zone, evidenced floristic relationships with other rocky outcrops in more humid areas, suggesting that habitat type is important for selecting specific groups, following the theory of refuges.

Effect of Shrub Components on Soil Water and Its Response to Precipitation at Different Time Scales in the Loess Plateau.

Water shortages have become the major limiting factor for ecological protection and sustainable development in the Loess Plateau. Few studies have focused on the effects of different plant components on soil water and its response to precipitation at different time scales. This study conducted an observation of shrub plants with three treatments (natural condition (NC), canopy + roots after removing the litter (CR), and only roots (OR)) to monitor the dynamics of soil water during the rainy season of an extreme drought year in 2015. The results showed that the soil moisture content (SMC) and soil water storage (W) had a trend of OR > CR > NC. The response of the SMC to precipitation was gradually decreased and delayed for longer with increasing soil depth. Daily precipitation >10 mm was the threshold to trigger an SMC response below 20 cm of depth. The thresholds of precipitation to increase W were 2.09-2.54 mm at the daily scale and 29.40-32.56 mm at the monthly scale. The effect of precipitation on W and its change (∆W) also depended on the time scales. At the daily scale, precipitation only explained 1.6%, 0.9%, and 2.4% of the W variation in NC, CR, and OR, respectively. However, precipitation was more important for ∆W, making a contribution of 57.6%, 46.2%, and 56.6%, respectively, and the positive ∆W induced by precipitation happened more easily and frequently at deeper depths in OR. At the monthly scale, the contribution of precipitation to ∆W increased to 75.0%, 85.0%, and 86%, respectively. The ∆W of the whole rainy season was OR > NC > CR. Precipitation of the monthly scale displayed higher contributions to soil water than that of the daily scale. Plant components had different influences on soil water and its response to precipitation, which was strengthened by the roots, weakened by the canopy, and neutralized by the litter. Regular cutting of the canopy at the single-shrub scale may help increase water storage, which is useful for vegetation management and hydrologic regulation.

Vegetation dynamics and soil nutrients across different shifting cultivation fallows in Montane Subtropical Forest of Mizoram, NE India

The objective of the present study is to understand the forest recovery and soil replenishment of fallow after shifting cultivation. Currently, the cycle of shifting cultivation has been shortened to 3–4 years, which affects the recovery potential of the forest. So, it is important to study the changes in vegetation and soil nutrient status in fallow areas of different ages. Based on the year of abandonment, 12 experimental plots of 30 m × 30 m were established, 4 shifting-cultivation fallows (FP) (i.e., 0–3, 4–7, 8–11 and 12–15 years old) and another 3 experimental plots were established in natural undisturbed forest (NF) for comparison. Phytosociological indices and soil properties were studied to understand the changes in relation to fallow age.Species composition varied among the fallow ages. The 12–15 year old FP had the highest number of tree individuals as well as number of species among all FP. The study showed an increase in the tree component, while the herbaceous and shrub component decreased with increasing age of FP, and the major effect was noticeable after 11 years FP. Soil properties differed significantly among all the study sites. Our study shows that longer the FP, the higher is the forest recovery and soil replenishment of fallows.

Floristic mosaics of the threatened Brazilian campo rupestre

The increase in rates of habitat loss requires an understanding of how biodiversity is distributed. Campo rupestre is an old, climatically buffered, and infertile landscape located in Brazil. Considered a biodiversity hotspot, the campo rupestre is mainly threatened by mining activity that requires a large operating area. Campo rupestre is known for its restricted distribution area and high abiotic heterogeneity, which modulates species coexistence and richness. To recognise the association between habitat type and plant communities, we propose to describe the floristic composition of herbaceous and shrub components in four habitats of the campo rupestre comprising quartzite and ferruginous substrate. We classified habitat types by the main surface soil features. In each habitat, we sampled ten 100-m2 plots to access information on the shrub and ten 1-m2 plots for the herbaceous component. Altogether we sampled 153 species, belonging to 38 families. The cluster analysis ordered by Sorensen metric indicates a clear distinction of species composition in the shrub component in the four habitats. However, the floristic composition of the herbaceous component was similar between the four habitats but showed a distinction when contrasting with the substrate type. Our results highlight the local taxonomic distinction between habitat types and substrates, indicating that the ecological distinction among substrate types of the campo rupestre cannot be overlooked in conservation and restoration actions.

The role of brush encroachment in Mediterranean ecosystems: a review

Abstract Encroachment of woody plants into grasslands and subsequent brush management are among the most prominent changes occurring in arid and semiarid ecosystems over the past century. The reduced number of farms, the abandonment of marginal land and the decline of traditional farming practices have led to encroachment of the woody and shrubby components into grasslands. This phenomenon, specifically in the Mediterranean region, which is followed by a reduction in herbage production, biodiversity and increased fire risk, is generally considered an undesirable process. Sarcopoterium spinosum has had great success in the eastern Mediterranean as a colonizer and dominant bush species on a wide variety of sites and climatic conditions. In the Mediterranean dehesa, the high magnitude and intensity of shrub encroachment effects on pastures and on tree production were shown to be dependent on temporal variation. Accordingly, there are attempts to transform shrublands into grassland-woodland matrices by using different techniques. The main management interventions that are commonly used include grazing, woodcutting, shrub control with herbicides or by mechanical means, amelioration of plant mineral deficits in the soil, and fire. However, the effects of these various treatments on the shrubs under diverse environmental conditions were found to be largely context-specific. As such, the most efficient option for suppressing encroachment of shrubs is combining different interventions. Appropriate management of grazing, periodic control of the shrub component, and occasional soil nutrient amelioration can lead to the development of attractive open woodland with a productive herbaceous understory that provides a wider range of ecological services.

Holocene expansion of the Caledonian pinewoods: Spatial and temporal patterns at regional and landscape scales

Background : To facilitate climatic change adaptation, landscape and conservation managers require understanding of spatio-temporal patterns of expansion of potential dominant species. Studying past expansions of canopy-dominant trees can contribute such understanding. Aims : Test hypotheses about expansions of dominants using as a model the mid-Holocene expansion of forests dominated by Pinus sylvestris in the Scottish Highlands. Methods : Pollen analysis and radiocarbon dating of Holocene sediments of a larger basin and several small hollows were performed in three landscapes along a north–south transect. A larger basin records expansion timing at landscape scale, whilst small hollows evidence within-landscape spatio-temporal patterns. Results : Vegetation existing prior to the expansion of pinewoods influenced landscape-scale spatio-temporal expansion patterns of P. sylvestris. Open vegetation generally was invaded earlier and/or to a greater extent; invasion was often later, or did not occur, where woodland with a substantial temperate broadleaved tree and shrub component (e.g. Corylus avellana, Quercus spp.) was present. Most small hollows, not just those where pinewoods became locally established, recorded vegetation change during the expansion. Some present landscape-scale forest composition patterns were established at that time. Conclusions : Studying past expansions of dominants provides evidence relevant to planning conservation and landscape management to facilitate ecological adaptation as species adjust their distributions and abundances in response to climatic change.

Aboveground Biomass Allocation of Boreal Shrubs and Short-Stature Trees in Northwestern Canada

In this follow-on study on aboveground biomass of shrubs and short-stature trees, we provide plant component aboveground biomass (herein ‘AGB’) as well as plant component AGB allometric models for five common boreal shrub and four common boreal short-stature tree genera/species. The analyzed plant components consist of stem, branch, and leaf organs. We found similar ratios of component biomass to total AGB for stems, branches, and leaves amongst shrubs and deciduous tree genera/species across the southern Northwest Territories, while the evergreen Picea genus differed in the biomass allocation to aboveground plant organs compared to the deciduous genera/species. Shrub component AGB allometric models were derived using the three-dimensional variable volume as predictor, determined as the sum of line-intercept cover, upper foliage width, and maximum height above ground. Tree component AGB was modeled using the cross-sectional area of the stem diameter as predictor variable, measured at 0.30 m along the stem length. For shrub component AGB, we achieved better model fits for stem biomass (60.33 g ≤ RMSE ≤ 163.59 g; 0.651 ≤ R2 ≤ 0.885) compared to leaf biomass (12.62 g ≤ RMSE ≤ 35.04 g; 0.380 ≤ R2 ≤ 0.735), as has been reported by others. For short-stature trees, leaf biomass predictions resulted in similar model fits (18.21 g ≤ RMSE ≤ 70.0 g; 0.702 ≤ R2 ≤ 0.882) compared to branch biomass (6.88 g ≤ RMSE ≤ 45.08 g; 0.736 ≤ R2 ≤ 0.923) and only slightly better model fits for stem biomass (30.87 g ≤ RMSE ≤ 11.72 g; 0.887 ≤ R2 ≤ 0.960), which suggests that leaf AGB of short-stature trees (<4.5 m) can be more accurately predicted using cross-sectional area as opposed to diameter at breast height for tall-stature trees. Our multi-species shrub and short-stature tree allometric models showed promising results for predicting plant component AGB, which can be utilized for remote sensing applications where plant functional types cannot always be distinguished. This study provides critical information on plant AGB allocation as well as component AGB modeling, required for understanding boreal AGB and aboveground carbon pools within the dynamic and rapidly changing Taiga Plains and Taiga Shield ecozones. In addition, the structural information and component AGB equations are important for integrating shrubs and short-stature tree AGB into carbon accounting strategies in order to improve our understanding of the rapidly changing boreal ecosystem function.

Temporal Rhythms of Dry Tropical Forest Regeneration under Exploration of Granite-Gnaisse Mining in a Semi-Arid Area

This research aims to identify and analyze the level of regeneration of Caatinga vegetation in different stages, under the impact of granite-gneiss mining in a semi-arid region in Northeast Brazil. To carry out the floristic and phytosociological survey, four areas of vegetation cover were selected in different stages of regeneration: 20 years (closed bush shrubland); 15 years (open bush shrub); 10 years (sub-shrub Caatinga); 50 years (reference area with shrubby Caatinga). The species records of the four sampled areas were compared using the Jaccard and Sorensen similarity index. For the phytosociological analysis, the parameters of Basal Area, Absolute and Relative Density, Absolute and Relative Dominance and Coverage Value of the species were calculated. The floristic survey registered 5,494 individuals belonging to 14 families and 34 species. It was found that Euphorbiaceae and Fabaceae were the families that contributed with the largest number of species in the tree and shrub components. The species in the areas where there was exploitation 20 and 15 years ago showed a regeneration process close to that registered in the preservation area for 50 years. However, with respect to wealth, the 20-year area showed the greatest abundance. From the results it was possible to know the process of regeneration of the pioneer and secondary successional species in the Caatinga, contributing to the preservation of the species and the recovery of degraded areas in the semi-arid region of Paraíba.

Disentangling the effects of multiple fires on spatially interspersed sagebrush (Artemisia spp.) communities

AbstractQuestionsRelative to a landscape with a mosaic of two sagebrush community types and increasing fire frequency, we asked: (a) do vegetation characteristics vary significantly with number of times burned for each sagebrush community; (b) how do vegetation responses to different fire frequencies compare between the two sagebrush communities?LocationColumbia Plateau Ecoregion, Washington, USA.MethodsWe sampled vegetation across a landscape that burned three times over a 10‐year period in two sagebrush community types that are interspersed on unique land forms: big sagebrush (Artemisia tridentata) communities that occur on small “mounds” and scabland sagebrush (A. rigida) communities that occur on surrounding “flats.” Spatially overlapping fires permitted a balanced sampling design to assess unburned and once‐, twice‐, and thrice‐burned locations for each land form/community type. We utilized a suite of statistical analyses to determine differences among plant functional groups and biomass among unburned/burned strata by land form and compared results between land forms.ResultsBig sagebrush and scabland sagebrush communities responded uniquely to multiple fires, due to different fuel loadings, fire severities, succession and invasion dynamics. Big sagebrush experienced nearly complete shrub loss and conversion from exotic‐invaded shrubland to exotic annual grassland after only one fire. In contrast, scabland sagebrush retained a minor shrub component and higher relative cover of native herbaceous species, even after three fires. Both communities retained cover of native perennial grasses, including shallow‐ and deep‐rooted species, likely reflecting decreasing fire intensity with number of times burned.ConclusionsDespite different community‐level responses, increasing fire frequency is transforming the entire landscape to a non‐native/native grassland mix. Quantifying unique ecosystem responses to altered wildfire regimes is critical to understanding the relative resilience of communities to disturbance and their resistance to exotic species invasion (and community type conversion). Management actions may help to maintain spatial heterogeneity of ecosystems and fire‐tolerant native species.

Plant diversity and botanical composition in an Atlantic heather-gorse dominated understory after horse grazing suspension: Comparison of a continuous and rotational management

Floristic diversity changes substantially depending on the type of land management. We evaluated the impact of a continuous (CG) and rotational (RG) grazing system on the dynamics of plant diversity and community composition in a heather-gorse understory after a two and six-year pause from horse grazing. Previously grazed sites had higher total and rare species richness and diversity than ungrazed (UN), regardless the type of grazing system. The positive impact of previous grazing on species richness was higher in CG and continued after six years in both grazing systems. Seven species of high conservation interest in heathlands were present in the studied areas. Most of them were associated to CG management and none was exclusively in RG. The reduction of the shrub component by previous horse grazing led to a decrease of gorse dominance, thus potentially reducing fire risk and increasing plant diversity. The extent of the positive effect of horse grazing controlling excessive accumulation of combustible material and favoring species richness differed when relative abundance of species, and not solely the number of species, was taken into account (Simpson’s dominance increased and Pielou’s evenness decreased after six years). Overall, the effects of previous rotational and continuous grazing on plant diversity in an Atlantic heather-gorse dominated plant community were still apparent 2 or 6 years after grazing interruption, although declined after the six-year grazing interlude. Rotational management revealed a slight advantage upon the control of gorse biomass long term, and assisted to maintain the relative abundance of species more evenly over time. The alpha and beta diversity indices confirmed that plant diversity similarity between rotational and continuous management increased after six years.

Biomass partitioning and allometric relations of the Reaumuria soongorica shrub in Alxa steppe desert in NW China

Allometry and partitioning of above- and below-ground biomass are needed to evaluate the sustainability of arid ecosystems. Biomass accumulation, allocation patterns, and allometric relationships for above- and below-ground components of the desert shrub Reaumuria soongorica were studied across five age classes (0–10, 11–20, 21–30, 31–40, and > 40 years) in Alxa desert steppe, northwestern (NW) China, where the biomass of each shrub component (i.e., leaves, branches, and coarse and fine roots) was harvested by destructive sampling and the allocation patterns between leaves (ML), roots (MR), branches (MB) were studied by regression analysis of log10-transformed data, and tested for data classified by age class and pooled data. By using basal diameter, age, height, and canopy area, we can predict the allometry properties of the R. soongorica shrub in terms of age class and/or entire age-sequence. The experimental results indicate that biomass accumulation has an obvious gradient across the five age classes, branch, and coarse root biomass were the main biomass pool as mature shrub. R. soongorica shrub partitioned a greater proportion of total biomass to roots with age in order to adapt to the extreme arid conditions. Shrub allometry was affected by variation of biomass partitioning, where the allometric relationships were strongly related to basal shrub diameter for almost all shrub components. Allometric biomass relationships were improved with the introduction of a second variable crown area.

Coenofloras of deciduous shrubs (Fruticeta foliosa) and shrub steppes (Steppa fruticeta) in the Black Sea part of Inhulets river basin

We revealed the composition of the coenotaxa of the shrub and shrub-steppe components of natural vegetation cover in the lower reaches of Inhulets river. For analyzing, we used 209 geobotanical releves collected during 1998–2017. Classification schemes of vegetation were created basing on the dominant approach. The article shows that the class of deciduous shrubs is presented by 9 associations belonging to 4 formations – Crataegeta fallacinae, Pruneta stepposae, Rhamneta catharticae, Roseta corymbiferae, and the class of shrub steppes – by 17 associations belonging to 6 formations – Amygdaleta nanae, Caraganeta fruticis, C. scythicae, Chamaecytiseta granitici, Ephedreta distachyae and Genisteta scythicae. The most widespread formation among deciduous shrubs is Crataegeta fallacinae, and among shrub steppes – Chamaecytiseta granitici. The last one determines the specifics of the vegetation cover in this region; its communities demonstrate high degree of adaptation to carbonate content in soils as well as tolerance to moderate total salt content, which is completely unusual for communities formed by ligneous biomorphes.
 The specific richness of the coenoflora of deciduous shrubs (Fruticeta foliosa) is formed by 189 species, and one of the coenoflora of shrub steppes (Steppa fruticeta) by 261 species. The comparative analysis of the structures of the coenofloras showed their significant differences. The ranking order of families in the taxonomic spectrum of flora of shrub steppes, in its basic part, approaches to proportions which are peculiar to the flora of whole Northern Black Sea Area; the family Rosaceae occupying the second place in the similar spectrum for the class of deciduous shrubs makes this coenoflora closer to floras of Central Europe. The characteristic feature of the flora of deciduous shrubs is the dominance of species of Palaearctic area type (25,8%), but, in the flora of shrub steppes, species of Black Sea area type (29,1%) prevail; it suggests that the core of the latter flora is original and indigenous. In contrast to the flora of deciduous shrubs where subshrubs are absolutely absent, the role of this biomorphe considerably increases within the composition of shrub steppes (up to 5,7%). The analysis of the ecologic structure of the investigated coenofloras showed that xeromesophytes prevail in the hygrospectrum of deciduous shrubs and euxerophytes do in the hygrospectrum of shrub steppes. In ecologic and coenotic spectra of both coenofloras, steppant species absolutely dominate: it is natural for shrub steppes and reflects the amphicoenotic character of deciduous shrubs.

INFLUÊNCIA DA TOPOGRAFIA E DA ABERTURA DO DOSSEL NA ESTRUTURA DO COMPONENTE HERBÁCEO-ARBUSTIVO EM DOIS FRAGMENTOS FLORESTAIS NA PLANÍCIE DE INUNDAÇÃO DO ALTO RIO PARANÁ

As florestas secundárias têm se expandido significativamente nos últimos anos. Dada a importância que as mesmas têm assumido nos planos de restauração e conservação, um entendimento mais abrangente sobre sua organização e funcionamento, levando em consideração as diferentes formas de vida, torna-se necessário. A fim de comparar a composição e estrutura do componente herbáceo-arbustivo entre dois fragmentos florestais com diferentes idades (RFID- remanescente florestal e FLT- floresta de 57 anos), bem como a influência relativa da topografia e abertura do dossel na organização da comunidade, dados vegetacionais e ambientais foram obtidos em 24 parcelas contíguas em cada área. Utilizaram-se correlogramas I de Moran e testes de Mantel parcial para verificar a correlação entre dados da comunidade e variáveis ambientais. Para testar diferenças entre as áreas amostrais aplicaram-se testes t de Student. As lianas mostraram-se espacialmente estruturadas (agregadas) em ambos os ambientes com um padrão semelhante ao observado para cota média. No RFID, as distâncias de cota média correlacionaram-se positivamente com as distâncias das matrizes, densidade de arbóreas e riqueza total e negativamente com as distâncias da matriz densidade de herbáceas, na FLT correlações significativas foram observadas somente entre as distâncias da matriz, densidade de arbóreas e as distâncias de desnível máximo e entre distâncias dos dados de cota e distâncias da matriz de riqueza total. Somente o componente arbustivo e abertura do dossel não apresentaram diferença significativa entre as duas áreas. A estrutura do estrato herbáceo-arbustivo tem se mostrado associada mais fortemente às características topográficas que à abertura do dossel.

Population Structure and Site Characteristics of the Rare Shasta Snow-Wreath (Neviusia cliftonii)

The Shasta snow-wreath (Neviusia cliftonii Shevock, Ertter & D.W. Taylor; Rosaceae) is a rare shrub, endemic to areas near Shasta Lake in the eastern Klamath Range of northern California, USA. Since discovery in 1992, the number of known populations has increased from 3 to 33. Shasta snow-wreath is a thicket-forming shrub, thought to reproduce primarily vegetatively, where individual stems (ramets) arise from the root system. We provide the first descriptions of demography and site characteristics using data collected in eight populations of Shasta snow-wreath. We established permanently-marked transects and recorded the number of ramets, individual stem heights, and the number of inflorescences in 2011, 2012, and 2013. We also characterized sites by tree canopy, shrub components, fuels, vegetation, and ground cover. Using the number of ramets recorded and the total population area, we estimated the number of ramets in each population (‘ramet population size'). Ramet population size ranged from 716 to 18,641 (mean = 5467), and the average maximum stem height ranged from 50 to 159 cm (mean = 104 cm). Larger ramet population size and taller stems were both associated with less tree cover. The two largest ramet population sizes were found at the two highest elevations and most west-facing sites. The average number of inflorescences per stem over three years ranged from 0.08 to 4.91 (mean = 2.76) and showed an increase with elevation. How Shasta snow-wreath will respond to succession or disturbances is unknown, but the negative relationship of ramet population size and canopy cover indicates that fire may have been important for influencing the population size historically. Continued monitoring of the studied populations, and the addition of more populations to the monitoring program, would be useful for detecting demographic changes and for better understanding the factors that govern Shasta snow-wreath.

Short-Term Response of Vegetation and the Riparian Bird Community to Dam Removal on the Rogue River, Oregon

Both establishment and subsequent removal of dams inevitably alter river systems and may impact aquatic and terrestrial organisms. Despite both stated and implicit restoration goals of dam removal, relatively few studies have examined ecological response. Using a before-after-control-impact framework one year before and two years after, I evaluated the short-term effect of a dam removal on the Rogue River in southwestern Oregon on vegetation, bird community composition, and abundance of eight riparian-associated bird species. No differences were detected for tree and shrub strata cover after dam removal for either treatments or controls. Within the three treatment habitat types (mainstem, slough, wetland), shrub and ground cover declined only in wetland areas, likely as a result of post dam removal vegetation management. Significant changes in relative abundance were found for only one of eight focal bird species. Chamaea fasciata (Wrentit) abundance declined on treatment points following dam removal, possibly a response to the decrease in cover of the shrub and ground vegetative strata in the wetland. Bird community composition did not differ between controls and treatments either before or after dam removal. In combination, the similarities in bird community composition and lack of detectable change in abundance for seven riparian associated species are consistent with the results for vegetative cover, suggesting shrub and tree components of riparian habitat did not change substantially in the two years following dam removal. Results from this study have important management implications for maintaining or restoring riparian vegetation in conjunction with future dam removals.

Vegetative Characteristics of Sage-grouse Nesting and Brood Rearing Sites

Vegetative characteristics of 146 greater sage-grouse (Centrocercus urophasianus) nest sites and 48 brood rearing sites were compared with paired random sites to determine if hens were selecting sites with certain vegetative attributes at three study areas in central Montana in 2003 and 2004. Ninety-seven percent of all nest locations and 92% of all brood rearing locations were in Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) plants. Therefore, only attributes of Wyoming big sagebrush plants were analyzed. Shrub characteristics such as percent cover, density (shrubs/m2), average shrub height (cm), nest shrub height (cm) and nest shrub production (g/shrub) were recorded. Herbaceous measurements such as forb cover (%), grass cover (%), total cover (%) and grass height (cm) were recorded. Sage-grouse hen nest sites had greater (P ≤ 0.05) average shrub height (36 vs 31 cm) and more (P ≤ 0.05) nest shrub production (55 vs 48 g/shrub) than random sites. There were no differences in sagebrush cover density or nest shrub height or any herbaceous characteristics between nest and random sites. Fifty percent of all nests were successful. Successful nest sites were not different from unsuccessful nest sites in any shrub or herbaceous component. There were no differences in shrub or herbaceous measurements between yearling and adult nest sites. Shrub and herbaceous characteristics of brood sites did not differ from random sites. Average shrub height was greater (P ≤ 0.05) for adult brood rearing sites compared to yearling sites (35 vs 31 cm). Brood site shrub cover was less (P < 0.05) than nest shrub cover (14 vs 21%). Our results suggest that even though nesting sage-grouse hens selected for taller and more productive Wyoming big sagebrush plants, these attributes did not improve nesting success. Grazing guidelines suggested to increase herbaceous vegetation may not improve nesting or brood rearing success. Although brood rearing vegetative characteristics were lower (P £ 0.05) in sagebrush cover and production than nesting sites, managers should not reduce Wyoming big sagebrush cover or production to emphasize one stage of sage-grouse production since this plant is vital for all life phases.

Relationships between hyperspectral data and components of vegetation biomass in Low Arctic tundra communities at Ivotuk, Alaska

Warming in the Arctic has resulted in a lengthening of the growing season and changes to the distribution and composition of tundra vegetation including increased biomass quantities in the Low Arctic. Biomass has commonly been estimated using broad-band greenness indices such as NDVI; however, vegetation changes in the Arctic are occurring at spatial scales within a few meters. The aim of this paper is to assess the ability of hyperspectral remote sensing data to estimate biomass quantities among different plant tissue type categories at the North Slope site of Ivotuk, Alaska. Hand-held hyperspectral data and harvested biomass measurements were collected during the 1999 growing season. A subset of the data was used as a training set, and was regressed against the hyperspectral bands using LASSO. LASSO is a modification of SPLS and is a variable selection technique that is useful in studies with high collinearity among predictor variables such as hyperspectral remote sensing. The resulting equations were then used to predict biomass quantities for the remaining Ivotuk data. The majority of significant biomass-spectra relationships (65%) were for shrubs categories during all times of the growing season and bands in the blue, green, and red edge wavelength regions of the spectrum. The ability to identify unique biomass-spectra relationships per community is decreased at the height of the growing season when shrubs obscure lower-lying vegetation such as mosses. The results of this study support previous research arguing that shrubs are dominant controls over spectral reflectance in Low Arctic communities and that this dominance results in an increased ability to estimate shrub component biomass over other plant functional types.

Plant production along a grazing gradient in a semiarid Patagonian rangeland, Argentina

Fil: Campanella, Maria Victoria. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Centro Nacional Patagonico. Instituto Patagonico para el Estudio de los Ecosistemas Continentales; Argentina