Herbaceous Layer Species Research Articles

Succession of a natural desert vegetation community after long-term fencing at the edge of a desert oasis in northwest China.

Fencing is the most economical method of restoring degraded desert ecosystems, and plays an important role in promoting plant community diversity and productivity, as well as stable ecosystem structure and function. In this study, we selected a typical degraded desert plant community (Reaumuria songorica-Nitraria tangutorum) on the edge of a desert oasis in the Hexi Corridor in northwest China. We then investigated succession in this plant community and corresponding changes in soil physical and chemical characteristics over 10 years of fencing restoration to analyze the mutual feedback mechanisms. The results showed that: 1) The diversity of plant species in the community increased significantly over the study period, especially the number of herbaceous layer species, which increased from four in the early stage to seven in the late stage. The dominant species also changed, with the dominant shrub layer species shifting from N. sphaerocarpa in the early stage to R. songarica in the late stage. The dominant herbaceous layer species changed from the annual herb Suaeda glauca in the early stage to S. glauca and Artemisia scoparia in the middle stage, and ultimately to A. scoparia and Halogeton arachnoideus in the late stage. In the late stage, Zygophyllum mucronatum, H. arachnoideus, and Eragrostis minor began to invade, and the density of perennial herbs also increased significantly (from 0.01 m-2 to 0.17 m-2 for Z. kansuense in year seven). 2) As the duration of fencing increased, the soil organic matter (SOM) and total nitrogen (TN) contents first decreased then increased, whereas the available nitrogen, potassium, and phosphorus contents showed the opposite trend. 3) Changes in community diversity were mainly affected by the nursing effects of the shrub layer, as well as soil physical and chemical properties. That is, fencing significantly increased the vegetation density of the shrub layer, which promoted growth and development of the herbaceous layer. However, community species diversity was positively correlated with SOM and TN. The diversity of the shrub layer was positively correlated with the water content of deep soil, whereas that of the herbaceous layer was positively correlated with SOM, TN, and soil pH. The SOM content in the later stage of fencing was 1.1 times that in the early stage of fencing. Thus, fencing restored the density of the dominant shrub species and significantly increased species diversity, especially in the herb layer. Studying plant community succession and soil environmental factors under long-term fencing restoration is highly significant for understanding community vegetation restoration and ecological environment reconstruction at the edge of desert oases.

放猪干扰对四川夹金山植物群落特征和生物量的影响

选择四川省夹金山针阔混交林，采用典型样地法调查、RDA二维排序分析高山高地植物群落的物种多样性与地上地下生产力的关系及两者对不同等级放猪干扰的响应，结果显示：（1）夹金山针阔混交林群落共有植物55科117属172种，乔木层、灌木层在各程度干扰下优势种变动较小，川滇长尾槭（Acer caudatum var.prattii）、箭竹（Fargesia spathacea）等始终占据首要地位，草本层优势种变化较大；（2）随干扰程度增加，一年生草本重要值升高，多年生草本重要值降低，其中适口性较强的禾草类植物重要值降低，且草本层地下与地上生物量比值明显降低；（3）乔灌草三层物种多样性水平在轻度干扰下最高，重度干扰下最低；（4） RDA结果分析显示，灌、草本层各物种多样指数（除Pielou均匀度指数外）与各层次生物量呈正相关，乔木层各多样性指数与灌木层地上地下生物量、枯落物量均呈正相关；（5）轻度干扰梯度下幼苗占比显著高于其他干扰梯度，I级下林内几乎未发现成活的乔木优势种幼树，群落更新能力最差。综上，建议将重度、较重度（Ⅱ级）干扰样地（即距养猪场2000 m范围内）的管理措施设置为禁牧或轮牧，重点维护川滇长尾槭、糙皮桦（Betula utilis）的幼树生长以促进更新。;The coniferous and broad-leaved mixed forest in Jiajin Mountain, Sichuan Province was selected to analyze the relationship between the species diversity of the alpine vegetation community and the aboveground and underground productivity and the response of the two to different levels of grazing disturbance by using typical sampling method and DCA two-dimensional ordering. The results showed that:(1) there were 172 species of trees, shrubs and herbs belonging to 55 families and 117 genera in the coniferous and broad-leaved mixed forest communities of Jiajin Mountain. The dominant species in the tree layer and shrub layer changed little under various levels of disturbance, and Acer caudatum var. prattii and Fargesia spathacea always occupied the first place, while the dominant species in herbaceous layer changed greatly; (2) With the increase of the grazing disturbance (from Ⅳ to Ⅰ), the important value of annual herbs increased, while that of perennial herbs decreased, and that of gramineous grasses decreased. The ratio of underground to aboveground biomass in herbaceous layer decreased significantly; (3) The species diversity level of tree, shrub and herbs was the highest under the level IV and the lowest under the level I; (4) The results of redundancy analysis showed that the species diversity index of shrubs and herbs (except Pielou evenness index J_sw) was positively correlated with the biomass of each layer, and the diversity indexes of tree layer were positively correlated with the aboveground and underground biomass of shrub layer and litter fall; (5) The proportion of saplings under level IV was significantly higher than that under other levels. But there were almost no dominant saplings in the forest under severe disturbance (level I), so the regeneration ability of the community was the worst. It is recommended to set the management measures for Ⅰ and Ⅱ (that is, within 2000 m from the pig farm) to grazing prohibition or rotation grazing, and focus on maintaining the growth of saplings of Acer caudatum var. prattii and Betula utilis to promote the regeneration of vegetation communities.

The effect of soil on spatial variation of the herbaceous layer modulated by overstorey in an Eastern European poplar-willow forest

Abstract The tree species composition can influence the dynamics of herbaceous species and enhance the spatial heterogeneity of the soil. But there is very little evidence on how both overstorey structure and soil properties affect the spatial variation of the herb layer. The aim of this study is to evaluate the factors of the soil and overstorey structure by which it is possible to explain the fine-scale variation of herbaceous layer communities in an Eastern European poplar-willow forest. The research was conducted in the “Dnipro-Orils’kiy” Nature Reserve (Ukraine). The research polygon (48°30′51″N, 34°49″02″E) was laid in an Eastern European poplar-willow forest in the floodplain of the River Protich, which is a left inflow of the River Dnipro. The site consists of 7 transects. Each transect was made up of 15 test points. The distance between rows in the site was 3 m. At the site, we established a plot of 45×21 m, with 105 subplots of 3×3 m organized in a regular grid. The adjacent subplots were in close proximity. Vascular plant species lists were recorded at each 3×3 m subplot along with visual estimates of species cover using the nine-degree Braun-Blanquet scale. Within the plot, all woody stems ≥ 1 cm in diameter at breast height were measured and mapped. Dixon’s segregation index was calculated for tree species to quantify their relative spatial mixing. Based on geobotanical descriptions, a phytoindicative assessment of environmental factors according to the Didukh scale was made. The redundancy analysis was used for the analysis of variance in the herbaceous layer species composition. The geographic coordinates of sampling locations were used to generate a set of orthogonal eigenvector-based spatial variables. Two measurements of the overstorey spatial structure were applied: the distances from the nearest tree of each species and the distance based on the evaluation of spatial density of point objects, which are separate trees. In both cases, the distance matrix of sampling locations was calculated, which provided the opportunity to generate eigenvector-based spatial variables. A kernel smoothed intensity function was used to compute the density of the trees’ spatial distribution from the point patterns’ data. Gaussian kernel functions with various bandwidths were used. The coordinates of sampling locations in the space obtained after the conversion of the trees’ spatial distribution densities were used to generate a set of orthogonal eigenvector-based spatial variables, each of them representing a pattern of particular scale within the extent of the bandwidth area structured according to distance and reciprocal placement of the trees. An overall test of random labelling reveals the total nonrandom distribution of the tree stems within the site. The unexplained variation consists of 43.8%. The variation explained solely by soil variables is equal to 15.5%, while the variation explained both by spatial and soil variables is 18.0%. The measure of the overstorey spatial structure, which is based on the evaluation of its density enables us to obtain different estimations depending on the bandwidth. The bandwidth affects the explanatory capacity of the tree stand. A considerable part of the plant community variation explained by soil factors was spatially structured. The orthogonal eigenvector-based spatial variables (dbMEMs) approach can be extended to quantifying the effect of forest structures on the herbaceous layer community. The measure of the overstorey spatial structure, which is based on the evaluation of its density, was very useful in explaining herbaceous layer community variation.

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.

The importance of beech forests as reservoirs of moth diversity in Mediterranean Basin (Lepidoptera)

Study analyzes the macrolepidoptera assemblages in beech woodlands of the Orsomarso Mountains (Pollino National Park, Southern Italy) to assess the role of beech forests in preserving diversity in Mediterranean Basin. Research was run between 2015 and 2016 in 15 stands representative of the main successional stages of forest maturation, placed between 990 and 1,475 meters of elevation. Monthlybased sampling was performed using UV-LED light traps. A total of 33,957 individuals belonging to 410 species was collected. The community is rich and the most abundant and characteristic species (Eilema lurideola, Operophtera fagata, Campaea margaritata) are almost all trophically linked to broadleaves or lichens. The community structure appears fairly constant and recognizable in all stands over the two years of sampling. Young beech forests hosted the greatest number of species compared to other forest maturation stages, though the difference is small. The greatest differences in the community structure are found in the clearings, where generalist and/or related to the herbaceous layer species are mostly represented. Biogeographically widely distributed species prevail, 87% of them having European or Asian-European distribution. There are a number of species of faunistic interest, among which Perizoma juracolaria, Chelis maculosa, Tiliacea citrago, Poecilocampa populi, Triphosa dubitata, Sideridis reticulata, Nebula senectaria, including 13 Italian endemics such as Coenotephria antonii. Populations of many species show significant genetic diversities compared to other European populations. The Orsomarso Mountains beech forests represent an important biodiversity reservoir, even at the genetic level, and show a good degree of naturalness.

Effects of excess nitrogen on biogeochemistry of a temperate hardwood forest: Evidence of nutrient redistribution by a forest understory species

Excess nitrogen (N) in terrestrial ecosystems can arise from anthropogenically-increased atmospheric N deposition, a phenomenon common in eastern US forests. In spite of decreased N emissions over recent years, atmospheric concentrations of reactive N remain high in areas within this region. Excess N in forests has been shown to alter biogeochemical cycling of essential plant nutrients primarily via enhanced production and leaching of nitrate, which leads to loss of base cations from the soil. The purpose of our study was to investigate this phenomenon using a multifaceted approach to examine foliar nutrients of two herbaceous layer species in one N-treated watershed (WS3—receiving aerial applications of 35 kg N/ha/yr as ammonium sulfate, from 1989 to the present) and two untreated reference watersheds at the Fernow Experimental Forest, WV, USA. In 1993, we analyzed foliar tissue of Viola rotundifolia, a dominant herb layer species and prominent on all seven sample plots in each watershed. In 2013 and 2014, we used foliar tissue from Rubus allegheniensis, which had become the predominant species on WS3 and had increased, though to a lesser extent, in cover on both reference watersheds. Foliar N and potassium (K) were higher and foliar calcium (Ca) was lower on WS3 than on the reference watersheds for both species. Magnesium (Mg) was lower on WS3 for Viola, but was not different among watersheds for Rubus. Results support the stream chemistry-based observation that excess N lowers plant-available Ca and, to a lesser degree, Mg, but not of K. Foliar manganese (Mn) of Rubus averaged >4 times that of Viola, and was >50% higher on WS3 than on the reference watersheds. A Mn-based mechanism is proposed for the N-meditated increase in Rubus on WS3. Data suggest that excess N deposition not only alters herb community composition and biogeochemical cycling of forest ecosystems, but can do so simultaneously and interactively.

Browsing intensity of herbaceous forbs across a semi-arid savanna catenal sequence

Ecological models to explain savanna heterogeneity and functioning weakly represent herbaceous forbs, which inevitably created knowledge gaps regarding the diversity and ecology of forbs. Forbs constitute over 70% of semi-arid savanna species richness. The aim of this study was therefore to (i) identify forb species that potentially form part of herbivore diet, and (ii) determine forb browsing intensity across a granitic savanna catenal sequence. Localized contrasts between nutrient-poor dystrophic uplands and nutrient-rich eutrophic bottomlands led us to predict that bottomlands would host forb assemblages dominated by browsed species. Forbs contributed to 78% of the total herbaceous layer species richness, of which 43% were browsed at varying intensities along the catenal sequence. Each topographic zone hosted a unique assemblage of browsed forbs, although browsing intensity was highest in the sodic bottomlands. Some browsed forbs formed prostrate, stoloniferous covers on the bottomlands, creating a lawn type dominated by forbs. Results presented here are the first to identify browsed forb species and to illustrate the turnover in browsing intensity of forbs across a semi-arid savanna catenal sequence. Our results add weight to the need to include herbaceous forbs in savanna management models to better understand savanna resource ecology and heterogeneity.

Restoration Results for a Maryland Shale Barren after Pignut Hickory Management and a Prescribed Burn

ABSTRACT Maryland shale barren (savanna) communities support rare, threatened, and endangered species, but biodiversity conservation sites are transitioning to pignut hickory woodland and forest as a result of fire exclusion. In Green Ridge State Forest, an exemplary community was studied for vegetation change after pignut hickory management and a prescribed burn. Portions of contiguous chestnut oak (Quercus montana) and streamside hardwood communities were also included. Prerestoration herbaceous layer characteristics were quantified in 2010 using transect plots before hickories were killed by herbicide. A prescribed burn was conducted in November 2011 followed by resampling in 2013. In the barren community, Carex pensylvanica remained the dominant herbaceous layer species, but codominant species changed. Ground cover increased from 63% to 76%, species richness from 48 to 52, and the Shannon-Wiener diversity index (H′) from 3.138 to 3.373. In the chestnut oak forest, the dominant herbaceous layer specie...

Long-Term Effects of High Intensity Prescribed Fire on Vegetation Dynamics in the Wine Spring Creek Watershed, Western North Carolina, USA

We examined the long-term effects of a prescribed fire in a southern Appalachian watershed in Nantahala National Forest, western North Carolina, USA. Fire was prescribed in 1995 on this site by forest managers to restore a degraded pine (Pinus spp.)-hardwood community, specifically to stimulate forage production, promote pine and oak (Quercus spp.) regeneration, and increase plant diversity. Before and after the prescribed fire, permanent plots were sampled across a south-facing hillslope, which corresponded to three community types: mesic, near-stream cove (riparian); dry, mixed-oak (mid-slope); and xeric, pine-hardwood (ridge). In an earlier paper, we reported the first two years of post-burn vegetation response from this prescribed burn. In our current study, we compared the pre-burn (1994) forest condition with 10 years post-burn (2005) vegetation measurements to determine the effects of fire on the mortality and regeneration of overstory trees, understory shrubs, and herbaceous-layer species. Overstory mortality was high immediately after the burn at the ridge location and ten years after the fire. Mortality of pitch pine (Pinus rigida Miller) (91.8 %) and hickory (Carya spp.) (77.5 %) reduced overstory basal area from 26.97 m2 ha−1 pre-burn to 18.86 m2 ha−1 post-burn in 1995 and to 9.13 m2 ha−1 in 2005. At the mid-slope and riparian locations, no significant overstory mortality occurred over time. Understory density was significantly higher 10 years after the burn (2005) than pre-burn, and basal area had returned to pre-burn levels. Density of mountain laurel (Kalmia latifolia L.), black huckleberry (Gaylussacia baccata [Wang.] K. Koch), and blueberry (Vaccinium spp.) had increased due to prolific sprouting. The prescribed fire had varying effects on diversity across the hillslope gradient over time. On the ridge, overstory diversity declined following the fire (H’basal area = 1.14 in 1994, H’basal area = 0.75 in 1995, and H’basal area = 0.80 in 2005). Diversity significantly increased in the herbaceous layer and remained higher than pre-burn conditions through 2005 (H’cover = 1.02 in 1994, H’cover = 1.97 in 1995, and H’cover = 2.25 in 2005). For the mid-slope and riparian positions, no change in diversity was observed in the overstory, understory or herbaceous layer.

Short-term response of the herbaceous layer within leave patches after harvest

Leave patches, uncut areas in a harvested forest, may conserve herbaceous layer species that decline after forest clearcutting. They may also serve to maintain source populations for the recolonization of the harvest area. The main objective of this study is to characterize the short-term response of the herbaceous layer to clearcut harvesting disturbance within and adjacent to leave patches. Four experimental 1 ha patches and two uncut references were established. Within each patch or reference, belts of five 1 m 2 quadrats were placed at 50 m and 5 m outside the patch, at 0 m (edge), and at 25 m, 35 m, and 50 m (centre) inside. These belts of quadrats were replicated at all four aspects (North, South, East, and West). Ground vegetation was sampled yearly for 1 year before harvest and 3 years after harvest in the experimental patches and for 2 consecutive years in the references. Some common residual species declined significantly in the clearcuts, but remained stable inside the patches in the short term (3 years after harvest). Overall species composition changed little in the patch interior and edge after harvest. Colonizing species (those that appeared in quadrats after harvest) in the patch exterior were predominantly early-seral species, whereas colonizers in the patch interior tended to be shade-tolerant forest species. Species were grouped a priori based on two habitat preferences (amounts of canopy cover and disturbed substrate). Species characteristic of a habitat with closed canopy and undisturbed substrates that decreased significantly over time in the patch exterior were negatively correlated with the amount of exposed mineral soil and open canopy. Species characteristic of a habitat with open canopy and disturbed substrates that increased significantly at the patch exterior showed a positive correlation with the amount of exposed mineral soil and open canopy. No species’ habitat preference groups declined significantly in the patch interior or edge over time. Based on species’ responses to forest operations, it appears that at least the common forest species are maintained in the short term within leave patches.

Ecological role of mountain ridges in and around gwangneung royal tomb forest in central Korea

We assessed the ecological structure and function of mountain ridges connected to a reserve area, Gwangneung Royal Tomb Forest (GRTF), in central Korea. This site has been strictly preserved since the 15th century. Our objectives were to 1 ) investigate the interactions between and the influence of a protected old-growth forest on its surrounding forests, and 2) suggest management strategies for forests outside that reserve area. Three ridges were surveyed and divided into two categories — A and B ridges covered with secondary forests connected to GRTF, and the C ridge, covered with primary forests and plantations within GRTF (from core zone to managed zone). The ridge forests had a characteristic lobe shape. We found no significant decline in species richness (peninsular effect) with distance from GRTF for any tree-layer or herbaceous-layer species on Ridges A or B. However, when only the species that appeared in primary forests on the C ridge were considered, the richness of tree- and herbaceous-layer species was significantly decreased there. This meant that the neighboring forests of GRTF could serve as a buffer zone. Differences were obvious between the two categorized forests in their species composition, species richness, basal area, and regeneration patterns. DCA ordination of quadrats on Ridges A and B showed that Axis 1 was significantly correlated with distance from GRTF, indicating that this protected area affects regeneration within neighboring forests. Thus, reserves are important not only to the conservation of biodiversity, but also to the ecological management of surrounding forests.

Plant diversity of secondary forests in response to anthropogenic disturbance levels in montane regions of northeastern China

The effects of anthropogenic disturbances on forest structure and plant diversity of secondary forest ecosystems were evaluated based on the classification by site factors in the montane regions of northeastern China. Forty-five sample plots containing 720 sub-plots of overstory species (8 m × 8 m), 1,440 quadrats of understory species (2 m × 2 m), and 1,440 quadrats of herbaceous layer species (1 m × 1 m) were clustered into five groups (G1, G2, G3, G4 and G5) by site variables with Hierarchical Cluster Analysis. Meanwhile, the disturbance levels corresponding to the five groups were determined according to the factors influencing human disturbances (D0-G2, D1-G1, D2-G3, D3-G5, and D4-G4). Species diversities of overstory, understory, herbaceous layer and overall species were evaluated using species number, Margalef index, Pielou index, Shannon–Wiener index, and Simpson index; and β-diversities (Whittaker index, Cody index). Basal area of stands exhibited a decreasing trend along the disturbance level due to a gradual increase in the extraction of timber by the human disturbances. The indices of species diversity suggested that overstory and understory species were distributed evenly among the groups or disturbance levels. There were no absolutely dominant tree species in the secondary forest ecosystems. The differences in site factors and the current disturbance intensities were not intense enough to lead to loose changes in overstory and understory species. The species diversity indices exhibited the maximum values at D3 (G5) for herbaceous layer species; this may suggest that the current disturbance intensities were intense enough to lead the changes of herbaceous layer species. Three rare and endangered species (Juglans mandshurica, Fraxinus mandshurica and Acanthopanax senticosus) were found within the secondary forests. These rare and endangered species appeared in each clustered group or disturbance level, which suggested that the current disturbance intensity in the study area was not strong enough to influence the distribution of rare and endangered species. The current disturbances in the secondary forests may not lead to a decrease in stability and complexity of the overstory and understory species, but the higher disturbance level may be intense enough to change the habitat fitness for the herbaceous species.

The effects of three regeneration harvest methods on plant diversity and soil characteristics in the southern Appalachians

We evaluated the effects of three regeneration harvest methods on plant diversity and soil resource availability in mixed-hardwood ecosystems. The study area is in the Wine Spring Creek watershed on the Nantahala National Forest of the Southern Appalachian Mountains in western North Carolina. The regeneration treatments were: an irregular, two-aged shelterwood cut (2A), with 5.0 m 2/ha residual basal area; a shelterwood cut (SW), with 9.0 m 2/ha residual basal area; a group selection cut (GS), with 0.10–0.20 ha openings and 25% overstory removal on area basis at first entry; fourth, the control, consisted of two uncut sites (UC). Each harvest treatment was replicated three times across the landscape in similar plant community types. Within each treatment area, permanent plots were marked and inventoried for overstory, midstory, and herbaceous layer plants. In each permanent plot, we collected soil samples in winter (December–March) to reduce temporal variation due to vegetation phenological stage and rainfall events. We analyzed soil samples for extractable calcium (Ca), magnesium (Mg), potassium (K), cation exchange capacity (CEC), pH, bulk density, A-horizon depth, total carbon (C), and nitrogen (N). Species diversity of overstory, understory, and herbaceous layer species was evaluated using species richness ( S), Shannon–Wiener's index of diversity ( H′), and Pielou's evenness index ( E). We used direct gradient analysis (non-metric multidimensional scaling, NMS) to explore the changes in vegetation–site relationships among herbaceous layer abundance, and soil characteristics and overstory basal area between pre-harvest (1994) and post-harvest (2000). Twelve minor overstory species were cut from the 2A treatments and nine species were cut from the SW treatments. Thus, it is not surprising that S and H′ were reduced in the overstory on the heavily cut sites. However, most of these species sprouted from cut stumps and were substantially more abundant in the midstory layer after harvest than before. For the midstory, we found higher S and H′ on the harvested treatments than the control; however, H′ did not differ significantly among the harvest treatments. We measured an increase in herbaceous layer H′ on the more heavily cut treatments (2A and SW) after harvest. We found an increase in average distance in the NMS ordination among sites in 2000 compared to 1994, which suggests greater herbaceous species diversity after harvest. However, we did not see a clear separation among harvest treatments in the NMS ordination.

Forest Understory Vegetation along a Productivity Gradient

these communities. We examined vegetation structure and species distribution patterns in the forest understory community of two topographically similar watersheds to evaluate the predicted roles of abiotic limitation and competition along a productivity gradient. Canonical correspondence analysis identified a dominant compositional gradient that was strongly correlated with moisture, light, and herbaceous-layer cover. Given these relationships, the first axis of the ordination was taken as a reliable index of productivity. Contrary to expectation, species richness increased monotonically along the gradient rather than reaching a maximum and then declining which suggests that species are not excluded by light competition at the high-productivity end of the gradient. Other vegetation patterns, however, indicated both abiotic limitation in regions of low productivity and competition at high productivity. Patterns in species' distributions also suggested resource limitation at low productivity, but they showed mixed evidence of competition at high productivity. Taken together, these patterns in vegetation structure and species' distributions imply that while competition may occur among herbaceous-layer species, particularly at high productivity, competitive exclusion remains low. This may be because the traits that permit survival under tree canopy shading reduce the effects of light competition with other understory species, or because understory productivity is not high enough to induce intense light competition among herbaceouslayer species.

Vegetation and fire readiness in main morphological units of Niokolo Koba National Park (Southeast Senegal)

Bush fires are the main cause of natural resource degradation in Niokolo Koba National Park. So-called “early fires” or management fires are considered an irreplaceable tool for land management in protected areas. A synthesis of the literature and field observation reveals that plateaus and slopes are the most prone to burning. Fire proneness depends mainly on vegetation characteristics. The main vegetation types on plateaus and slopes are shrub and arboreal savannah, respectively. These savannah types are both dominated by Combretaceae in the ligneous stratum, while in the herbaceous layer species of Poaceae family dominate. The predominance and state of Poaceae in the herbaceous layer are major indicators of fire readiness. It is sought to adopt a strategy for early fire implementation that minimizes impact on natural resources. Any strategy must include an operational system for monitoring herbaceous fuel conditions. Such a system could benefit from new remote sensing technologies when combined with field measurements in the most exposed zones.

Herbaceous Layer Contrast and Alien Plant Occurrence in Utility Corridors and Riparian Forests of the Allegheny High Plateau

communities by alien plant species that can adversely affect community structure and function. To determine how corridor establishment influences riparian vegetation of the Allegheny High Plateau of northwestern Pennsylvania, we compared the species composition and richness of the herbaceous layer (all vascular plants s 1 m tall) of utility corridors and adjacent headwater riparian forests, and tested the hypothesis that utility corridors serve as foci for the invasion of adjacent riparian forest by alien vascular plants. We contrasted plant species richness and vegetative cover, cover by growth form, species richness and cover of alien plants and cover of microhabitat components (open soil, rock, leaf litter, log, bryophyte) in utility corridors and adjacent riparian forest at 17 sites. Cluster analysis revealed that herbaceous layer species assemblages in corridors and riparian forest were compositionally distinct. Herbaceous layer cover and species richness were significantly (P s 0.05) greater in corridors than in riparian forest. Fern, graminoid, and forb species co-dominated herbaceous layer cover in corridors; fern cover dominated riparian forests. Cover of alien plants was significantly greater in corridors than in riparian forest. Alien plant species richness and cover were significantly and positively correlated with open soil, floodplain width, and active channel width in corridors but were significantly and negatively correlated with litter cover in riparian forest. Given that the majority of alien plant species we found in corridors were shade-intolerant and absent from riparian forests, we conclude that open utility corridors primarily serve as habitat refugia, rather than as invasion foci, for alien plant species in riparian forests of the Allegheny High Plateau.

Sampling to Assess Species Diversity of Herbaceous Layer Vegetation in Allegheny Hardwood Forests

The optimum frequency and time of sampling required to generate comprehensive diversity indices of herbaceous species in Allegheny hardwood forests was studied. Four 8-ha sites on the Allegheny National Forest were sampled monthly from May to August in 1992 and 1993 for herbaceous layer species composition and percent cover.

Herbaceous Layer and Soil Response to Experimental Acidification in a Central Appalachian Hardwood Forest

AbstractThe herbaceous layer (vascular plants ≤1 in in height) is an important component of forest ecosystems and a potentially sensitive vegetation stratum in response to acid deposition. This study tested several hypotheses concerning soil and herbaceous layer response to experimental acidification at the Fernow Experimental Forest in north‐central West Virginia. Fifteen circular sample plots (0.04 ha) were established in each of three watersheds: WS3 (an ≈ 20‐yr‐old watershed receiving acidification treatment with (NH4)2SO4), WS4 (&gt;80‐yr‐old control), and WS7 (≈ 20‐yr‐old control). The herb layer was sampled intensively in 10 1‐m2 subplots within each sample plot, including determination of species composition, cover, and random biomass harvests. Harvested plant material was separated by species and analyzed for macronutrients, micronutrients, and Al. Soft was sampled from harvest subplots and analyzed for texture, pH, organic matter, and macro‐ and micronutrients. Few differences among watersheds for virtually all measured soil variables indicated minimal response of soil fertility to the acidification treatment. The herbaceous layer was also quite similar among watersheds with respect to cover‐biomass and species diversity; WS7, however, had ≈ 70% higher herb layer cover that both Ws3 and WS4, a result of the predominance of a few high‐cover fern species and attributable to the north‐facing aspect of WS7 vs. south‐facing aspects of WS3/WS4. There was a high degree of species similarity among watersheds, suggesting no shift in species composition in response to acidification. There was also minimal response of element concentrations to acidification, although Fe and Al exhibited evidence of increased uptake in WS3. We conclude that, contrary to our expectations, there has been little substantive response of the soil and herb layer to acidification, but hypothesize that herbaceous layer species may experience toxicity problems with increased mobility of Al and micronutrients in the future.

Vegetation structure, natural regeneration and management of Parroha community forest in Rupandehi district, Nepal

Understanding vegetation structure and regeneration in community forests in important for management planning. The present work was done during September to October 2005. The information on forest management practices was collected by Participatory Rural Appraisal (PRA) which included field observation, interviews and focus group discussion. A total of 125 plant species belonging to 55 families with 36 tree species, 50 shrubs and 39 herbs were recorded from the 0.7 ha sampling area. The total tree density and basal area at South-East (SE) facing slope was 595 pl/ha and 29.68 m²/ha, respectively, where Terminalia alata was the most dominant with highest importance value index (IVI). On the other hand, total tree density and basal area was 453 pl/ha and 41.78 m²/ha, respectively, at South-West (SW) facing slope, where Shorea robusta was the most dominant with the highest IVI. Total shrub/sapling density was 4708 pl/ha at SE slope and 4137 pl/ha at SW slope. Similarly, total herb/seedling density was 10.86 pl/m² at SE slope and 9.79 pl/m² at SW slope. The total number of tree species (S) in tree stage was higher at SE slope than at SW slope and the number of species in shrub layer was higher at SE slope than at SW slope. The two slopes had nearly equal number of species in herbaceous layer. Higher species diversity (H) of different lifeforms was found at SW slope. The SW slope had higher species evenness (J) and Simpson’s index of dominance (C) for all life forms than at SE slope. High similarity index for all tree, shrub/sapling and herb/seedling layers (63.63%, 84.61% and 77.10% respectively) were found between two sites. Alpha (α) diversity for shrub layer was higher at SE slope whereas beta (β) diversity for tree layer was higher at SW slope than at SE slope. Regeneration of Shorea robusta and Terminalia alata was continuous because density increased from tree, sapling to seedlings with a typical reverse J shaped size class diagram at both slope. But regeneration of S. robusta at SW slope was sporadic. The reccurence of forest fire during summer season has appeared as a major problem for the management of forest. The active participation of the local people in forest conservation activities can be effective for sustainable management of forest. Keywords: Community forestry; Vegetation; Regeneration; Size class diagram; Shorea robusta; Terminalia alata. DOI: http://dx.doi.org/10.3126/sw.v9i9.5523 SW 2011; 9(9): 70-81