Current Vegetation Composition Research Articles

Comparison of vegetation composition in an ephemeral stream channel and the perimeter of pools in subtropical subhumid Central Texas

AbstractEphemeral streams are common in sub‐humid central Texas, but have received little attention. Within ephemeral streams are isolated pools that contain water for longer periods than the channel. This study examined the vegetation composition in an ephemeral dry stream channel and pools in Leon Creek. Twelve sites within the dry channel and twelve ephemeral pools in Leon Creek were surveyed for vegetation between late March and mid‐May 2020 in central Texas, USA. Plant species were similar between the dry channel and pools over a 1.5 km distance indicating that habitats are similar in both allowing the occurrence of upland, facultative, and wetland plant species. A total of 114 species of multiple functional groups were documented in this study. Panicum virgatum had greater coverage at >20% in both the ephemeral channel and pools compared to all other plant species. Ten plant species were dominant with a mean coverage of >3% and no difference was observed for dominant species in the dry channel and pools. The coverage of perennial species were significantly greater in the dry channel and pools but annual coverage in the dry channel was similar to perennial coverage in the pools. Graminoids and forbs were significantly greater in coverage compared to trees, shrubs, vines, and ferns in both the dry channel and pools. Shrub and tree cover was rare accounting for <0.3% coverage. Native species coverage was significantly greater compared to non‐native species in the dry channel and pools. Droughts, flash floods, and scouring events appear to promote perennial graminoids and forbs dominance in Leon Creek with shrubs and trees being uncommon. The results of this study is the first to evaluate vegetation in an ephemeral channel and pools in central Texas and provides current vegetation composition providing information that can be used to compare changes to vegetation in the future.

Historical fire ecology and its effect on vegetation dynamics of the Lagunas de Montebello National Park, Chiapas, México

Historical information on wildfires and dendrochronological studies offer meaningful clues about fire and climate regimes, factors that affect forest structure and dynamics. This study aimed to determine the effect of fire history on vegetation dynamics and successional pathways of areas under different fire management policies in the Lagunas de Montebello National Park (LMNP), Chiapas, México. The selected study sites were El Parque area under fire exclusion policies since 1961; Tziscao-inhabited area under fire prohibition since 1984; and Antelá area with a traditional agricultural fire management history. A Pinus oocarpa ring-width chronology was used as a proxy for climate variability to which wildfire occurrence was mapped and to determine the establishment patterns of this dominant species. Current vegetation composition and structure and fuel loads were determined to characterise the study sites. Large wildfires, like those occurring in 1984 and 1998, were associated with periods of high humidity followed by intense droughts; they were linked to strong El Niño events and severely impacted the LMNP. Vegetation dynamics indicated simplification of mesophyll forest (climax) to pine-oak-sweetgum forests, with Pinus dominating the overstorey in all sampling sites. Pine, oak and sweetgum species were the dominant juvenile trees in Antelá, El Parque and Tziscao, respectively. Late-successional seedlings (i.e., Prunus) were present in Antelá and El Parque, while were absent from Tziscao where several wildfires had occurred. Fuel accumulation in sites within protected areas subject to fire exclusion policies was very high (40-68 t ha-1); in contrast, it was the lowest in rural Antelá (24 t ha-1). Considering vegetation vulnerability to wildfires associated with extreme humid-dry climate events, increased fire hazard due to fuel accumulation, and the socio-ecological impacts of these events, we recommend revising the fire exclusion policies currently implemented in the LMNP and applying an integrated fire management approach that incorporates local socio-ecological conditions.

Hydroclimate influences on modern pollen rain of upland southeastern Amazonia

For accurate interpretations of palaeopalynological data, it is important to understand the influence of the current vegetation composition and characteristics on the formation of the palynological assemblage recorded in artificial or natural pollen traps. Therefore, in this study, modern pollen rain was characterized using artificial pollen traps under different ecological conditions and climatic seasons in Trilha da Mata Lake, Carajás North Ridge, southeastern Amazonia. The collection of pollen rain data comprises the total period from September 2015 to August 2016. There were two periods of low rainfall (September to December 2015 and May to August 2016) and one period of high rainfall (January to April 2016). The first two periods were represented by a predominance of canga vegetation pollen relative to forest pollen. Under dry conditions, the associations among the taxa Aparisthmium/Alchornea, Myrcia and Bellucia dichotoma were considered important for forest ecosystems, while those among Pleroma, Hyptis parkeri, Borreria and Perama carajensis were considered important for canga ecosystems. Under wet conditions, the forests were well represented by Schefflera, Anthurium lindmanianum, Pseudopiptadenia suaveolens and Glycydendron, and the most represented canga vegetation in the pollen rain were Poaceae undif., Miconia, M. acutistipula var. ferrea and Psychotria. Aparisthmium/Alchornea and Poaceae undif. Aparisthmium/Alchornea was related to periods of low water availability, and Poaceae undif. was associated with marshy or flooded environments. Thus, an increase in the influx of Poaceae undif. pollen grains was determined by variations in the extension of flooded areas, indicating an increase in the amount of rainfall and not the opposite case. Thus, future studies on vegetation reconstruction must consider modern pollen assemblages to precisely determine paleoenvironmental and paleoclimate conditions during sediment deposition.

Modern botanical analogue of endangered Yak (Bos mutus) dung from India: Plausible linkage with extant and extinct megaherbivores.

The study reports the micro- and macrobotanical remains on wild Yak dung, providing evidence for understanding the diet, habitat, and ecology of extant and extinct megaherbivores. Grasses are the primary diet of the yak as indicated by the abundance of grass pollen and phytoliths. Other associated non-arboreal and arboreal taxa namely, Cyperacaeae, Rosaceae, Chenopodiaceae, Artemisia, Prunus, and Rhododendron are also important dietary plants for their living. The observation of plant macrobotanical remains especially the vegetative part and seeds of the grasses and Cyperaceae is also in agreement with the palynodata. The documented micro- and macrobotanical data are indicative of both Alpine meadow and steppe vegetation under cold and dry climate which exactly reflected the current vegetation composition and climate in the region. The recovery of Botryococcus, Arcella, and diatom was observed in trace amounts in the palynoassemblage which would have been incorporated in the dung through the ingestion of water and are indicative of the presence of perennial water system in the region. Energy dispersive spectroscopy analysis marked that the element contained in dung samples has variation in relation to the summer and winter, which might be due to the availability of the food plants and vegetation. This generated multiproxy data serves as a strong supplementary data for modern pollen and vegetation relationships based on surface soil samples in the region. The recorded multiproxy data could also be useful to interpret the relationship between the coprolites of herbivorous fauna and the palaeodietary, the palaeoecology in the region, and to correlate with other mega herbivores in a global context.

RELATIONSHIPS BETWEEN SOIL SEED BANK AND VEGETATION DIVERSITY ON DIFFERENT GRAZING PRESSURE

In a case study, the main objective was to compare three sites with different grazing pressures in Hvitarsida, W-Iceland in relation to current vegetation, seed bank composition and the correlation between those. Our results show that there were significant difference in species composition in above and belowground, giving very little similarity in species composition between seed bank and current vegetation composition. The only exceptions were Agrostis capillaris and Bistorta vivipara that had close similarity between current aboveground vegetation and soil seed bank. Agrostis capillaris had a great abundance in all the sites and Bistorta vivipara proliferates mostly with bulbils that most likely were numerous in the soil. The results of our study agree with current theories on seed bank composition and similar studies,that the similarity between current above ground vegetation and soil seed bank depends on current dominant species (annual or perennial)and the productivity (high or low) of the site.Mongolian Journal of Agricultural Sciences Vol.13(2) 2014: 105-113

Distribution and environmental requirements of stream habitat with Ranunculion fluitantis and Callitricho‐Batrachion vegetation in lower Belgium (Flanders)

ABSTRACTStreams with Ranunculion fluitantis and Callitricho‐Batrachion vegetation – or habitat type 3260 according to the European Habitats Directive – require particular conservation at biogeographic level but Member States carry individual responsibility. Within this framework, the environmental requirements of this habitat type in lower Belgium (Flanders) were analysed.Overall, current vegetation composition was not significantly related to adjacent land‐use but correlated mainly with physical–chemical conditions and to a lesser extent with distance to source and channel width. Even though sites with habitat 3260 generally showed lower levels of human impact, their abiotic features overlapped considerably with those of sites without habitat 3260 but still showing hydrophyte development.Thresholds occurred in the distribution of responsive macrophyte taxa, including the more common characteristic species of the habitat type, along gradients of increasing solutes and nutrients. Comparison with water quality standards proposed so far to support good ecological status for the European Water Framework Directive in lowland rivers suggests that compliance would probably allow this habitat to persist in most cases, although some discrepancies occur. This implies that more stringent objectives may be required in some water bodies.The present analysis focuses on the conditions delimiting occurrence of HT 3260, and therefore its range and area in lower Belgium. A comprehensive understanding of its favourable conservation status remains difficult in lowland regions where most rivers are subject to strong human impact and will require a more long‐term perspective that also considers management regime, physical habitat structure and connectivity. Copyright © 2014 John Wiley & Sons, Ltd.

Evaluating Southern Appalachian Forest Dynamics without Eastern Hemlock: Consequences of Herbivory by the Hemlock Woolly Adelgid

Eastern hemlock (Tsuga canadensis Carriére) and the Carolina hemlock (Tsuga caroliniana Engelmann) are ecologically important tree species in eastern North America forests that are currently threatened by the hemlock woolly adelgid (HWA, Adelges tsugae Annand, Hemiptera: Adelgidae). HWA has spread rapidly from its original introduction site into new areas. Once present, HWA kills its hosts over a period of 4 to 10 years leading to a phenomenon that is known scientifically and colloquially as hemlock decline. To date, quarantine, chemical management, and biocontrol efforts have failed to curb the spread of the HWA. As such, forest management efforts are now being redirected towards developing an understanding of the effects of hemlock removal on vegetation dynamics, changes in forest composition, and changes in ecosystem function. In this study, we parameterize a spatially explicit landscape simulation model LANDIS II for a specific forested region of the southern Appalachians. Parameterization involves defining the life-history attributes of 37 tree species occupying 11 ecological zones and is based on knowledge of: current vegetation composition data, recent historic management and fire regimes, and life-history traits of each species. The parameterized model is used to explore a simple scenario of catastrophic hemlock mortality likely to occur as a result of HWA herbivory. Our results emphasize that hemlock is an important foundation species. When hemlock is removed from the system, forest composition changes considerably with a greater presence of shade intolerant pine and oak species. Additionally, hemlock removal leads to a period of transient, relatively unstable vegetation dynamics as the forest communities restructure.

The peat-forming spring wetlands of the Strathbogie plateau - floristics and environmental relationships.

Spring wetlands on the Strathbogie plateau were mapped using recent aerial photography to estimate their current and former extent. The floristic composition and relationships of the vegetation with topographic, environmental and land use variables were interpreted from an analysis of quadrat data. Wetland condition, threats to their persistence and future management requirements were also identified. More than half of the original wetland vegetation in the study area appears to have been lost, probably as a result of clearing for agriculture. Nine floristic assemblages, identified using agglomerative hierarchical clustering, were identified on acidic to mildly alkaline peat in five different hydrogeomorphic settings. One of these assemblages (Low Open Sedgeland) was uniquely confined to spring-fed mounds, not previously described in Victoria. A key to identification of these groups was developed. Floristic composition was correlated with climate and site disturbance but charcoal throughout sediment cores suggested that historical disturbance regimes included fire. Forested sites at higher elevations where grazing pressure appears to have been less intense were the least disturbed sites. Approximately 60% of the wetlands surveyed were assessed as showing signs of soil moisture loss but there was no evidence that water extraction via dams and known bores was a significant driver of current vegetation composition. Threats requiring management were related to habitat destruction and degradation, dysfunction of physical and biological processes, and changes to disturbance regimes. Establishment of native vegetation buffers and biomass management are likely to be of benefit for future management of spring wetland vegetation.

The impacts and implications of an intensifying fire regime on Alaskan boreal forest composition and albedo

AbstractClimate warming and drying are modifying the fire dynamics of many boreal forests, moving them towards a regime with a higher frequency of extreme fire years characterized by large burns of high severity. Plot‐scale studies indicate that increased burn severity favors the recruitment of deciduous trees in the initial years following fire. Consequently, a set of biophysical effects of burn severity on postfire boreal successional trajectories at decadal timescales have been hypothesized. Prominent among these are a greater cover of deciduous tree species in intermediately aged stands after more severe burning, with associated implications for carbon and energy balances. Here we investigate whether the current vegetation composition of interior Alaska supports this hypothesis. A chronosequence of six decades of vegetation regrowth following fire was created using a database of burn scars, an existing forest biomass map, and maps of albedo and the deciduous fraction of vegetation that we derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery. The deciduous fraction map depicted the proportion of aboveground biomass in deciduous vegetation, derived using a RandomForest algorithm trained with field data sets (n=69, 71% variance explained). Analysis of the difference Normalized Burn Ratio, a remotely sensed index commonly used as an indicator of burn severity, indicated that burn size and ignition date can provide a proxy of burn severity for historical fires. LIDAR remote sensing and a bioclimatic model of evergreen forest distribution were used to further refine the stratification of the current landscape by burn severity. Our results show that since the 1950s, more severely burned areas in interior Alaska have produced a vegetation cohort that is characterized by greater deciduous biomass. We discuss the importance of this shift in vegetation composition due to climate‐induced changes in fire severity for carbon sequestration in forest biomass and surface reflectance (albedo), among other feedbacks to climate.

Vegetation dynamics related to sediment accumulation in Kushiro Mire, northeastern Japan

We investigated the relationship between vegetation changes and site condition in Kushiro Mire, northeastern Japan, where massive depositions of sediment from the watershed have been observed over the last several decades. These changes also included the changing area of floodplain forest. To determine the factors that induced the changing floodplain forest area and the effect of sediment accumulation on floodplain vegetation, we examined site conditions where vegetation had recently changed. We classified the pattern of vegetation change as new forest (formerly meadow), new meadow (formerly forest), stable forest (forest since 1967), and stable meadow (meadow since 1967) with the help of aerial photographs taken in 1967, 1977, and 2000. The survey results showed that the quadrats were divided into six vegetation types based on current vegetation composition. All new forests comprised alder (Alnus japonica) and were divided into two vegetation types. New meadows were also considered alder forest based on remnants of former forest and divided into two vegetation types. The site condition showed better correspondence to the pattern of vegetation change than the current vegetation composition, though it had a significant relationship with the latter. In new forests, high water table and a relatively high content of clay and silt characterized the site condition, whereas in new meadows, low water table and high sand content were the site characteristics. We discuss these site characteristics in the context of alder’s adaptability to site. It is suggested that coarse sediment probably along with intense flooding and fine sediment coupled with high water table contributed to the disappearance and establishment of alder forests, respectively.

PLANT COMPOSITION AND EROSION POTENTIAL OF A GRAZED WETLAND IN THE SALMON RIVER SUBBASIN, IDAHO

Wetlands are dynamic habitats with many unique, important functions including filtering sediments and providing diverse habitats for fish and wildlife. Wetlands in the western United States are particularly important because they offer habitat for a number of protected runs of endangered fish species. Historically, livestock grazing has altered wetland and riparian area form and function by facilitating exotic species invasions, altering spatial heterogeneity of vegetation, and increasing erosion. In this study we examined vegetation structure and erosion potential in a wetland meadow exposed to unregulated grazing along Deer Creek in the Salmon River subbasin, Idaho. We characterized the vegetation composition and structure within the study area and attempted to assess potential erosion conditions using the Revised Universal Soil Loss Equation (RUSLE), an empirical approach developed by the U.S. Department of Agriculture–Agricultural Research Service (USDA-ARS). We found no significant spatial variability in species richness and noted a moderate number of exotic species in the total plant composition. Plant cover was higher near slightly entrenched banks, indicating that uncontrolled livestock were primarily occupying gently sloped streambanks and the interior of the meadow. Based on current vegetation composition and RUSLE results, uncontrolled grazing may be negatively impacting the study area. If uncontrolled grazing were excluded or carefully managed in the wetland meadows of the upper portion of the Deer Creek watershed, a reduction in excess sediments to Deer Creek may occur.

Recent changes (1930s–1990s) in spatial patterns of interior northwest forests, USA

We characterized recent historical and current vegetation composition and structure of a representative sample of subwatersheds on all ownerships within the interior Columbia River basin and portions of the Klamath and Great Basins. For each selected subwatershed, we constructed historical and current vegetation maps from 1932 to 1966 and 1981 to 1993 aerial photos, respectively. Using the raw vegetation attributes, we classified and attributed cover types, structural classes, and potential vegetation types to individual patches within subwatersheds. We characterized change in vegetation spatial patterns using a suite of class and landscape metrics, and a spatial pattern analysis program. We then translated change in vegetation patterns to change in patterns of vulnerability to wildfires, smoke production, and 21 major forest pathogen and insect disturbances. Results of change analyses were reported for province-scale ecological reporting units (ERUs). Here, we highlight significant findings and discuss management implications. Twentieth century management activities significantly altered spatial patterns of physiognomies, cover types and structural conditions, and vulnerabilities to fire, insect, and pathogen disturbances. Forest land cover expanded in several ERUs, and woodland area expanded in most. Of all physiognomic conditions, shrubland area declined most due to cropland expansion, conversion to semi- and non-native herblands, and expansion of forests and woodlands. Shifts from early to late seral conifer species were evident in forests of most ERUs; patch sizes of forest cover types are now smaller, and current land cover is more fragmented. Landscape area in old multistory, old single story, and stand initiation forest structures declined with compensating increases in area and connectivity of dense, multilayered, intermediate forest structures. Patches with medium and large trees, regardless of their structural affiliation are currently less abundant on the landscape. Finally, basin forests are now dominated by shade-tolerant conifers, and exhibit elevated fuel loads and severe fire behavior attributes indicating expanded future roles of certain defoliators, bark beetles, root diseases, and stand replacement fires. Although well intentioned, 20th-century management practices did not account for landscape-scale patterns of living and dead vegetation that enable forest ecosystems to maintain their structure and organization through time, or for the disturbances that create and maintain them. Improved understanding of change in vegetation spatial patterns, causative factors, and links with disturbance processes will assist managers and policymakers in making informed decisions about how to address important ecosystem health issues.