Vegetation Community Structure Research Articles

Assessing the environmental sustainability of cultivation systems in wetlands using the WET-Health framework in Zimbabwe

This article assesses the environmental sustainability of cultivation systems in three selected communal wetlands in Zimbabwe using the WET-Health framework developed by Macfarlane et al. (2008). This research was motivated by the desire to provide baseline information critical for effective and robust wetland policy development, as monitoring of wetland ecological conditions is relatively poor despite high community dependence on them. The WET-Health framework is based on indicator and impact scores of (1) extent, (2) intensity, and (3) magnitude of impact of different land-use types on wetlands. Our results show that wetland degradation is caused principally by land-use activities in the wetland instead of those in the upstream catchment. The tillage system of broad ridges and broad furrows (BR/BF) caused wetland drying due to drainage and alteration of vegetation community structure and composition. However, BR/BF is effective in erosion control. It is therefore argued that, in general, the BR/BF tillage system does not contribute to sustainable wetland use as it disrupts the ecosystem’s hydrological functioning. Given the inherent subjectivity of the WET-Health method results, this study has shown that integration of spatial mapping techniques, such as high-resolution remotely sensed data, improves the quality of ecological assessment.

Macrophyte response to the protection and restoration measures of four water bodies

Macrophytes are a good long-term indicator of quality of aquatic ecosystems and are essential for the proper functioning of the entire lake ecosystem. Submerged vegetation is considered to be indicative of an improvement of the ecological status of these lakes. Here, we analyzed the distribution, structure, and diversity of vegetation communities in four eutrophic water bodies (postglacial lakes: Slawskie and Uzarzewskie and man-made lakes: Maltanski Reservoir and Turawa Średnia Reservoir) after the application of restauration and protections measures. The restoration measures included biomanipulation, phosphorus inactivation, hypolimnion aeration, or injection of nitrate-rich waters to the hypolimnion. All of them were sustainable and did not cause drastic changes in the ecosystem. Between 9 and 17 macrophyte communities were found in the examined water bodies. The largest effects were observed after the simultaneous use of three lake restoration techniques which led to the appearance of 17% charophytes. Pronounced effects leading to the higher contribution of elodeids to the macrophyte community were achieved in the lake in which two methods were applied. Least effective was the method focused on hypolimnion restoration in a small lake, which did not cause the reappearance of submerged vegetation. Spontaneous recovery achieving good status is also possible in a large lake in case of applying the thorough conservation measures. An intensive growth and diversity of macrophytes was a result of the improvement in the water quality as a consequence of undertaken protective activities and/or restoration measures. However, the re-colonization of submerged macrophytes during restoration process is not obvious and the feed-back mechanisms may delay a response of the ecosystem. The vegetation of the studied lakes was unstable, showing high variability in individual years of research, which indicates that these ecosystems are still under reconstruction and not reach equilibrium state yet.

Diversity, functional structure and functional redundancy of woodland plant communities: How do mixed tree species plantations compare with monocultures?

Managing forest plantation stands in a way that retains productivity targets, but that also fosters biodiversity and stand resilience are key sustainable forest management goals. Current forestry policy advocates a diversification of forest stands to achieve these goals, favouring mixed age structures and polycultures over single-aged monocultures. Evidence is lacking, however, to support this management recommendation for biodiversity gains and related ecosystem service delivery. We used indices of taxonomic diversity and functional structure to compare ground vegetation communities in mixed and pure stands of Scots pine (Pinus sylvestris) and pedunculate oak (Quercus robur) in each of three study regions. We categorised the 91 vascular plant species identified into functional effect and response groups. We tested the hypotheses that ground vegetation communities (i) differ significantly in structure and composition between Scots pine and oak monocultures and (ii) show enhanced levels of taxonomic and functional diversity and functional redundancy in mixed stands of Scots pine and oak compared with monocultures. We explored the implications of any differences in the functional structure of ground vegetation communities in the different stand types on two ecosystem services: nutrient availability and levels of resource provisioning for herbivores. Nine functional response groups (RG) and seven functional effect groups (EG) were identified with considerable overlap in the RG and EG species grouping. Three RGs had traits characteristic of forests (spring flowering herbs, tree saplings and shrubs/climbers), one RG had traits characteristic of open habitats (annual ruderals) and the remaining RGs had more generalist traits (anemochorous perennials, graminoids and short perennials). No significant differences were found among stand types in terms of taxonomic diversity or richness of the different functional trait groups. Ground vegetation communities in the three study regions also had similar levels of functional redundancy across stand types. However, Scots pine and oak monocultures harboured significantly different abundances of species with distinct functional traits. In all three study regions, anemochorous perennials were significantly more abundant in Scots pine monocultures than oak monocultures, while two core forest groups (shrubs/climbers, spring flowering herbs) were significantly more abundant in oak monocultures. Mixed stands had intermediate abundances of these functional groups. These differences have implications for the comparative availability of food resources and shelter for wildlife, but also the mobilisation and temporal availability of nutrients in the two monocultures. Thus, mixtures of Scots pine and pedunculate oak can temper significant tree species identity influences on ground vegetation functional diversity.

Soil characteristics and plant distribution in saline wetlands of Oued Righ, northeastern Algeria

Saline wetlands are rare ecosystems in Saharan areas, which are important for conservation of many endemic and rare plant species. In this study, we investigated five saline wetland sites of the Oued Righ region, located in the northeastern Algeria, to determine the environmental factors controlling the composition and distribution of plant communities. We established a total of 20 transects to measure the vegetation parameters (density and cover) and soil characteristics (electrical conductivity, moisture, pH, CaSO4, CaCO3, organic matter, Na+, K+, Mg2+, Ca2+, SO4 2–, Cl–, NO3 – and HCO3 –). A total of 17 plant species belonging to seven families were identified. The natural vegetation was composed of halophytic and hydro-halophytic plant communities, presented specially by the species of Amaranthaceae family. Soils in the studied wetlands were moist, gypsiferous, alkaline, salty to very salty with dominance of chloride and calcium. Results of the Canonical Correspondence Analysis (CCA) showed that community structure and species distribution patterns of vegetation were mainly dependent on soil characteristics, mainly being soil salinity (CaSO4, K+, Ca2+ and Cl–) and moisture. The distribution of plant species was found to follow a specific zonal pattern. Halocnemum strobilaceum was observed to grow in highly salt-affected soils, thus being the more salt-tolerant species. Phragmites communis plants were widely distributed in the study area with a high density at the edges of accumulated water body. Juncus maritimus, Tamarix gallica and Salicornia fructicosa grew in soils that are partially or completely flooded in winter. Suaeda fructicosa, Traganum nudatum, Arthrocnemum glaucum, Aeluropus littoralis, Cressa cretica and Cynodon dactylon were distributed in salty and moist soils away from the open water body. Plants of Zygophyllum album, Limonastrirum guyonianum, Cornulaca monacantha, Cistanche tinctoria, Mollugo nudicaulis and Sonchus maritimus were found in soils with less salty and moisture. They constituted the outermost belt of vegetation in the studied wetlands. This study will provide a reference on introducing the salt-tolerant plant species as a fodder resource in saline habitats and regenerating the degraded saline wetlands.

Long-term drainage reduces CO<sub>2</sub> uptake and increases CO<sub>2</sub> emission on a Siberian floodplain due to shifts in vegetation community and soil thermal characteristics

Abstract. With increasing air temperatures and changing precipitation patterns forecast for the Arctic over the coming decades, the thawing of ice-rich permafrost is expected to increasingly alter hydrological conditions by creating mosaics of wetter and drier areas. The objective of this study is to investigate how 10 years of lowered water table depths of wet floodplain ecosystems would affect CO2 fluxes measured using a closed chamber system, focusing on the role of long-term changes in soil thermal characteristics and vegetation community structure. Drainage diminishes the heat capacity and thermal conductivity of organic soil, leading to warmer soil temperatures in shallow layers during the daytime and colder soil temperatures in deeper layers, resulting in a reduction in thaw depths. These soil temperature changes can intensify growing-season heterotrophic respiration by up to 95 %. With decreased autotrophic respiration due to reduced gross primary production under these dry conditions, the differences in ecosystem respiration rates in the present study were 25 %. We also found that a decade-long drainage installation significantly increased shrub abundance, while decreasing Eriophorum angustifolium abundance resulted in Carex sp. dominance. These two changes had opposing influences on gross primary production during the growing season: while the increased abundance of shrubs slightly increased gross primary production, the replacement of E. angustifolium by Carex sp. significantly decreased it. With the effects of ecosystem respiration and gross primary production combined, net CO2 uptake rates varied between the two years, which can be attributed to Carex-dominated plots' sensitivity to climate. However, underlying processes showed consistent patterns: 10 years of drainage increased soil temperatures in shallow layers and replaced E. angustifolium by Carex sp., which increased CO2 emission and reduced CO2 uptake rates. During the non-growing season, drainage resulted in 4 times more CO2 emissions, with high sporadic fluxes; these fluxes were induced by soil temperatures, E. angustifolium abundance, and air pressure.

EFFECTS OF FIRE ON POPULATION DYNAMICS OF AN ENDEMIC HIGH ALTITUDE RUPICOLOUS GEOPHYTE

Stevia camporum (Asteraceae) is a threatened and endemic geophyte of the rocky outcrop vegetation in the high altitude grasslands on the top of the Itatiaia massif. This is a locally abundant plant, which establishes itself preferentially on vegetation mats dominated by pioneer species such as mosses (Campylopus pilifer) and by the vascular endemic plants Fernseea itatiaiae and Barbacenia gounelleana. With a very distinctive morphology, these nurse plants may differently influence the dynamics of S. camporum. These relations were previously studied for two years when a 3-day unnatural fire burned the grassy vegetation around the rocky outcrops, thereby affecting indirectly the vegetation mats (islands) growing at the exposed rocky surfaces, through ash emissions and changes on the availability of nutrients. We described pre-fire (1999-2001) and post-fire (2002-2003) population demography and growth of S. camporum under the hypothesis that Stevia demography would change due to effects of fire, such as nutrient income and, further, that responses would vary according to the dominant pioneer species of each vegetation mat. Forty-three islands containing S. camporum (total area of 30.08m2) were monitored. Despite considerable variation in rainfall between years, population structure and dynamics of S. camporum were very similar in the two pre-fire growing seasons. A massive increase in the frequency of branches in the first size class followed fire, but with nearly no changes in the other classes with a thinning process being observed. The height, number of nodes and number of fruits of Stevia camporum’s ramets showed significant differences when comparing the values for periods before and after the fire. Stevia’s demography on Fernseea (Bromeliaceae) mats was significantly different in relation to the other mat species, after fire. In Itatiaia, indirect effects of smoke produced by fire episodes seem to trigger rapid responses on rupicolous communities followed by rapid return to previous conditions, particularly in secondary species. Prolonged effects on more often disturbed communities remain to be seen, and might be relevant to community structure of high altitude outcrop vegetation.

Temporal Variation in Native Bee Diversity in the Tropical Sub-Deciduous Forest of the Yucatan Peninsula, Mexico

Native bee community diversity is known to vary temporally in the Neotropics, but little research has been done to quantify the extent of this variation. We studied monthly variation in native bee diversity in tropical semi-deciduous forest on the Yucatan Peninsula, Mexico, over a twelve-month period in 2007. Hurricane Dean traversed the study area in August of that year, causing some changes in the environment and in the native bee community. A total of 2,335 individual bee specimens were collected, belonging to 102 species from four families. The family Apidae had the highest number of species (46%) and individuals (71%). Species richness, abundance, and diversity varied throughout the study period. Species proportions of lifestyles and nesting behaviors varied from month to month, and absolute numbers changed. Low to moderate similarity values indicated high monthly species turnover, with almost half of species present for only one to two months. Species richness declined after the hurricane, with a loss of 40% of the species present beforehand, but nine new species appeared in September. The hurricane also reduced the number of solitary, parasocial, and social species, mostly those nesting in preexisting cavities and wood. Species composition in August had similarity values nearer to those of months in the dry season than to those in the rainy season. Two months after the hurricane, the native bee community had returned to previous species diversity levels, probably due to the rapid recovery of the vegetation on which the bee community depends. Effective biodiversity conservation programs will need more data on changes in vegetation community structure and how such changes influence Neotropical native bee communities after natural disturbances.

The soil and plant biogeochemistry sampling design for The National Ecological Observatory Network

AbstractHuman impacts on biogeochemical cycles are evident around the world, from changes to forest structure and function due to atmospheric deposition, to eutrophication of surface waters from agricultural effluent, and increasing concentrations of carbon dioxide (CO2) in the atmosphere. The National Ecological Observatory Network (NEON) will contribute to understanding human effects on biogeochemical cycles from local to continental scales. The broad NEON biogeochemistry measurement design focuses on measuring atmospheric deposition of reactive mineral compounds and CO2 fluxes, ecosystem carbon (C) and nutrient stocks, and surface water chemistry across 20 eco‐climatic domains within the United States for 30 yr. Herein, we present the rationale and plan for the ground‐based measurements of C and nutrients in soils and plants based on overarching or “high‐level” requirements agreed upon by the National Science Foundation and NEON. The resulting design incorporates early recommendations by expert review teams, as well as recent input from the larger natural sciences community that went into the formation and interpretation of the requirements, respectively. NEON's efforts will focus on a suite of data streams that will enable end‐users to study and predict changes to biogeochemical cycling and transfers within and across air, land, and water systems at regional to continental scales. At each NEON site, there will be an initial, one‐time effort to survey soil properties to 1 m (including soil texture, bulk density, pH, baseline chemistry) and vegetation community structure and diversity. A sampling program will follow, focused on capturing long‐term trends in soil C, nitrogen (N), and sulfur stocks, isotopic composition (of C and N), soil N transformation rates, phosphorus pools, and plant tissue chemistry and isotopic composition (of C and N). To this end, NEON will conduct extensive measurements of soils and plants within stratified random plots distributed across each site. The resulting data will be a new resource for members of the scientific community interested in addressing questions about long‐term changes in continental‐scale biogeochemical cycles, and is predicted to inspire further process‐based research.

STRUKTUR KOMUNITAS, ZONASI DAN KEANEKARAGAMAN HAYATI VEGETASI MANGROVE DI SEGARA ANAKAN CILACAP

Mangrove ecosystem of Segara Anakan Cilacap has specific vegetation, function, and benefit. It was dominated by Rhizophora, Bruguiera, Avicennia and associate vegetation such as Nypa frutican. Stability of mangrove ecosystem can be seen by community structure, zonation and diversity of mangrove vegetation. This research aimed to analyze community structure, zonnation and diversity of mangrove vegetation in Segara Anakan Lagoon. This research used survey method with cluster sampling by stratified analysis. The Analyze of data used association analysis, zonation analysis, richnes index, and Shanon Wiener index. This Research showed that (1) Association index of seedling was dominated by index < 0.22 (lowest association) with scored 46,67 % - 66.66 %, (2) Association index of sapling also was dominated by index < 0.22 (lowest association) with scored 58,33% - 71.43 %, (3) Association index of tress also was dominated by index < 0.22 (lowest association) with scored 67,27 % % (4) Overlaping indeks showed Aegiceras corniculatum has high overlap toward Nypa frutican (71 %) (seedling stage) and Rhizophora apiculata to Avicennia spp (0,49) (sapling stage). (5) Zonation of mangrove showed that Zone 1 as direct connecting zone with sea which were dominated by Avicennia marina and Avicennia oficinallis. Zone 2 as the middle zone which were dominated by Rhizophora mucronata, Rhizophora apiculata, and Ceriops tagal. Zone 3 as direct connecting zone with island which were dominated by Nypa fruticans, Acanthus ilicifolius, and Sonneratia casseolaris (6) diversity index between 0.48 – 1.83 (low – middle).Keywords : mangrove vegetation, acosiation index, zonation, community structure and diversity

Floristic Composition of Alabama Piedmont Floodplains across a Gradient of Stream Channel Incision

Abstract Stream channel incision in the Piedmont of the southeastern US has resulted in a loss of stream and floodplain functions. Reduced flood frequency and lowered water tables typify incised low-order streams of the region. The objective of this study was to determine if a quantifiable shift in riparian vegetation community structure exists along a gradient of channel incision. Stream channel incision was described using bank height ratio (BHR), defined as the ratio of streambank height to bankfull depth. Ten low-order streams in the Alabama Piedmont were selected across a gradient of BHR values (1.0–5.2). Stream incision is strongly correlated with a shift of community type in the ground flora stratum, from wetland-adapted species at low degrees of incision to plants typical of upland settings at incised sites. Based on Nonmetric Multidimensional Scaling (NMDS) ordinations, functional composition of the ground flora layer was significantly related to median groundwater depth and BHR. These results su...

침입외래식물인 가시박과 털물참새피에 의하여 교란된 하안식생

Biological invasion of alien plants is considered to be one of the most serious threats to biodiversity in riparian zones. The effects of two invasive alien plants, Sicyos angulatus and Paspalum distichum var. indutum, on the flora and community structure of the riparian vegetation were investigated at 22 sites at streams in Korea. Sicyos angulatus has invaded the central Korean Peninsula. This alien plant has caused problems to stream managers because of its aggressive vining growth. It had suppressed native vegetation such as trees, shrubs and tall grasses on bank slope and higher floodplains. Paspalum distichum var. indutum has become more widespread in the southern part of Korea. This invasive plant has shallow rhizomes and creeping, extensively branched stolons. It forms a dense mat over lotic or slowly-flowing water and threatens submerged and short emergent hydrophytes. In order to control the introduction and expansion of alien plants, limitation of artificial disturbances and appropriate alien plant management are needed in riparian areas.

Soil Nutrient Assessment and Characterization in a Degraded Central Florida Swamp

Flatford Swamp, a 2800-acre forested wetland in east Manatee County, Florida, serves as the headwaters of the Myakka River. Over the last two decades, Flatford swamp has experienced significant tree mortality. The cause of this mortality, as well as dramatic encroachment of several invasive herbaceous and shrub species, is thought to be linked to hydrologic alterations that resulted in increased inundation during the wet and dry seasons. A biogeochemical characterization of wetland soils was conducted to (1) establish a baseline spatial distribution of soil P and N in Flatford Swamp, (2) determine if soil biogeochemistry could be related to tree mortality, and (3) determine if soil biogeochemical conditions may affect future restoration efforts. Mean total nitrogen and total carbon in sampled soils ranged from 13.8 to 24.9 mg kg−1 and 211 to 468 mg kg−1, respectively, indicating that soils are predominantly organic. Environmental conditions suggest that the nitrate-reduction process occurs readily in Flatford Swamp, and thus N abatement will continue naturally during restoration. Soil total phosphorus content is significantly higher than expected and is likely one of several contributing factors that led to observed changes in vegetation community structure. Levels of total sulfur, total calcium, and conductivity, indicative of agricultural use of groundwater for irrigation, suggest sulfide toxicity as a plausible contributing mechanism in the observed dieback of Nyssa sylvatica var. biflora.

Heterogeneous flows foster heterogeneous assemblages: relationships between functional diversity and hydrological heterogeneity in riparian plant communities

Summary Riparian ecosystems are biophysically complex and highly diverse taxonomically, structurally and functionally. While many environmental factors determine the structure and function of riparian vegetation communities, hydrology is thought to be the ‘master variable’. Flooding and variability in water availability are known to be key drivers of taxonomic diversity, but their influence on the functional trait diversity of riparian vegetation communities remains largely unexplored. We collected data on species abundance, quantitative plant functional traits and hydrology from 15 sites distributed across south‐eastern Australia to address the following questions: (a) Is functional trait diversity related to the frequency and magnitude of flooding disturbance? (b) Is functional trait diversity related to variability in seasonal water availability within the riparian zone? We confirm that metrics describing both flooding disturbance and patterns of water availability exhibit strong relationships with functional trait diversity in riparian vegetation communities of south‐eastern Australia. Our key finding is that functional trait diversity in these systems tends to be positively associated with variability in hydrological conditions and the intensity of rare, high‐magnitude flooding events, rather than average patterns of flow. Our study highlights the importance of extreme flooding events and temporal patterns of water availability as determinants of diversity in riparian vegetation communities. These relationships may have significant consequences for plant communities experiencing alterations to hydrology caused by anthropogenic flow modification and the changing climate.

The relationship between successional vascular plant assemblages and associated microbial communities on coal mine spoil heaps

The aim of the study was to investigate the relationships between the vascular plant species and the associated soil microbial properties at various stages of vegetation development on unclaimed hard coal mine spoil heaps in Upper Silesia (south Poland). The spontaneous vegetation, soil chemistry as well as the activity and structure of microbial communities were recorded on this specific habitat. The colliery heaps were divided into four age classes and the plant species composition and cover abundance were recorded on established plots (2 m × 2 m). The soil microbial activity under the vegetation patches was assessed using fluorescein diacetate hydrolytic activity (FDHA) and the soil microbial biomass and community composition were determined by phospholipid fatty acid (PLFA) biomarkers. Total microbial biomass in soils from the older vegetation plots was significantly higher than those in soils from the younger plots. In all studied samples, microbial communities consisted primarily of bacteria with the dominance of Gram negative bacteria over Gram positive and aerobic microorganisms were more dominant than anaerobic ones. Statistical analysis revealed a correlation between the type of vegetation and microbial community structure.

Vegetation and climate change in the Beijing plain during the last million years and implications for Homo erectus occupation in North China

Beijing is of great significance in human evolution studies. However, the lack of well-dated records of climate and environmental changes, which are frequently cited as important drivers of early human evolution, impede understanding of the evolution and dispersal of humans on the Beijing plain. A 150-m deep drill core was collected from the Changping District of the Beijing plain to reconstruct the changes in vegetation and climate during the Middle Pleistocene using pollen records. The results indicated that the tree genus Ulmus and the herb genus Artemisia were dominant in most of the samples from 0.96 to 0.61 Ma, reflecting an open forest steppe covering the Beijing region. Between 0.61 and 0.44 Ma, the vegetation communities shifted to an Artemisia-steppe as the tree cover declined. This was followed by a further shift in vegetation community structure to a Chenopodiaceae-Asteraceae steppe between 0.44 and 0.23 Ma, followed by the conversion to an Artemisia-Asteraceae steppe after 0.23 Ma. The pollen record revealed a long-term deterioration of the vegetation, which indicated an increasing trend of drying and cooling in the Beijing plain during the Middle Pleistocene. This coincides with the Homo erectus colonization of North China during this period. These findings provide supporting evidence that a shift in climate towards cold and dry conditions during the Middle Pleistocene may have directly benefited Homo erectus populations in open habitats of North China. This general pattern of declining vegetation cover in the study area is consistent with climatic and environmental patterns in other regions of North China, which were probably influenced by global cooling during the Middle Pleistocene. (C) 2015 Elsevier B.V. All rights reserved.

Differential water and soil conservation capacity and associated processes in four forest ecosystems in Dianchi Watershed, Yunnan Province, China

The soil and water conservation capacity of forest ecosystems is closely associated with precipitation, runoff, sediment delivery, and the export of the nutrients nitrogen (N) and phosphorus (P) from forest soil. Research has investigated the potential for decreasing runoff pollution from watersheds by improving the function of forest ecosystems in conserving soil and water. Four typical forest ecological systems, including Pinus armandii forest, Yunnan pine forest, mixed broadleaf-conifer forest, and broad-leaved forest, were compared for vegetation community structure and species diversity; water-holding capacity in canopy, litter and soil layers; and the relationship with surface runoff and the export of sediment, N, and P during the 2013 rainy season. The species number and species richness were in the range of 10 to 22 and 4.68 to 7.94, respectively. The Shannon-Wiener Index, Simpson Index, and Pielou Index were 0.95 to 1.67, 0.43 to 0.68, and 0.50 to 1.04, respectively. Canopy interception rate increased with decreasing precipitation. The linear correlation equation of the two parameters was described as I = −2.768x + 64.318, where I = the canopy interception rate (mm) and x = rainfall amount (mm). The broad-leaved forest had the greatest interception rate because of its dense canopy. Litter storage in the four forest ecosystems ranged from 7.31 to 11.98 t ha−1 (6,527 to 10,698 lb ac−1); the highest litter yield was found in the broad-leaved forest. In this ecosystem, both the undecomposed and semidecomposed litter had the most water retention capacity (14.02 t ha−1 [12,519 lb ac−1] and 14.71 t ha−1 [13,136 lb ac−1], respectively) and effective water interception rate (8.18 t ha−1 [7,304 lb ac−1] and 9.01 t ha−1 [8,045 lb ac−1], respectively). In the 0 to 60 cm (0 to 23.6 in) soil layer, the broad-leaved forest had the greatest soil field capacity of 188.80 t ha−1 (168,598 lb ac−1) and 18.88 mm (0.74 in) water depth equivalent. The amount of surface runoff, sediment yield, and export of N and P increased with rainfall amounts, but the four forest ecosystems differed significantly in these properties. The ranges of sediment yield and export of total N and P were 13.1 to 344.2, 0.16 to 1.55, and 0.02 to 0.10 mg m−2, respectively. The broad-leaved forest formed an extremely dense canopy and had the highest maximum water-holding capacity, porosity, and soil field capacity. These properties made this ecosystem highly suitable for decreasing surface runoff and the export of sediments, N, and P from the forest soil.

English

The aim of this study was to determine the ecological characteristic of Namatimbili Forest in terms of plant species composition, stem size class structure, stand biomass, diversity, and distribution and identify endemic and threatened plant species that are found within the forest. Data were sampled by using transect method that were established in various habitats within the forest. A total of 312 plant species were found in 62 families, where Fabaceae (51 species) was the highly represented of all families. Of all plant species recorded, 26 are cited under IUCN red list and 36 are endemic species of East African Coastal Forests.The woodlands were more diverse with a Shannon’s index of 2.72 ± 0.21 followed by the riverine forest (1.64 ± 0.19), coral rags (2.28 ± 0.32) and closed canopy evergreen forest (2.32± 0.17) and this pattern was also applied to the species evenness and the difference among vegetation types was significant. The DCA ordination revealed a major variation at DCA-Axis1 where samples from riverine forest separated quite clearly and positioned on the right side of the ordination space. The coral rag habitat extended widely overlapping with other habitats because of high similarity in plant species composition. The woodland habitats separated from the evergreen forest habitat at DCA Axis 3 because of plant species composition differences between them, such that closed canopy trees and the understorey species characterized the evergreen habitats. The riverine forest had a density of 136 stems/ha with the DBH sizes between 41 and 292.99 cm and the stand biomass ranged from 0.1 to 876.06 m3/ha. However, high density of trees with DBH sizes beyond 90 cm was observed in the riverine forest, regardless of all the vegetation typeshaving individual stems beyond this size class. The coral rag vegetation had 42 stems/ha, with diameter at breast height (DBH) sizes ranging from 41 to 95.5 cm and stand biomass in a range from 0.1 to 59 m3/ha. The woodlands had 28 stems/ha with the DBH sizes between 41 and 77.38 cm with denser stems at the size class of 10-14 cm DBH and stand biomass in a range from 0.06 to 127.4 m3/ha. There were 31 stems/ha in the evergreen forest with the DBH sizes from 41.40 to 108.28 cm and stand biomass between 0.06 and 64.42 m3/ha. A significant difference exists in stand biomass, basal area, but no difference in crown cover among vegetation types. It can be concluded that, the heterogeneous habitat characteristics in Namatimbili Forest favour the performance of diverse plant species and determine their natural distribution patterns. Large proportion of plant species found in the forest is endemic to the East African Coastal Forests and some of these have been cited under various IUCN threat categories. However, exploitation of timber trees, fire, and clearance for cultivation negatively affected the plant species diversity, distribution and vegetation community structure in this forest. Based on the ecological importance of Namatimbili Forest, the forest need to be considered for gazetting for protection from habitat degradation caused by anthropogenic activities and it should be included in the natural resource management plans of the southern coastal forests of Tanzania. Key words: Namatimbili forest, coastal forests, endemic, habitas, threats, IUCN, anthropogenic disturbance.

Hyperspectral remote sensing of peatland floristic gradients

Previous studies have shown that the floristic composition of northern peatlands provides important information regarding ecosystem processes and their responses to environmental change. Remote sensing is the most expeditious method of obtaining floristic information at landscape and regional scales, but the spatial complexity of many northern peatlands and the spectral similarity of a number of peatland vegetation species is such that the success of traditional methods of vegetation classification is often limited. Here, we assessed whether ordination and regression analyses may be a useful alternative method for mapping peatland plant communities from remote sensing data. We used isometric feature mapping (Isomap) to describe the community structure of the peatland vegetation and related the identified continuous floristic gradients to hyperspectral imagery (AISA Eagle) using partial least squares regression (PLSR). We performed the same analysis at two hierarchical levels of species aggregation in order to map continuous gradients in the composition of both species and plant functional types (PFTs), the latter of which is the most widely used level of aggregation in northern ecosystems. Isomap was able to transfer 82% and more than 96% of the observed ground-based observations to the ordination space for plots characterised by species and PFT; respectively. The modelled floristic gradients showed good agreement with ground-based species and PFT observations although the strength of the agreement was proportional to the amount of floristic variation explained by each ordination axis (r2val=0.74, 0.45 and 0.30 for the first three ordination axes and r2val=0.68 and 0.66 for the first two ordination axes; for species and PFT floristic gradients respectively). We also found that how a PFT is defined has an important influence on the success with which it can be mapped. The resultant mapped floristic gradients enabled visualisation of homogeneous vegetation stands, heterogeneous mixtures of different key species and PFTs, and the presence of continuous and abrupt floristic transitions, without the need for unique spectral signatures or the collection of data characterising ancillary environmental variables.

Seed bank composition varies along invasion and inundation gradients in vernal pool wetlands

Environmental filters are well-known influences on aboveground vegetation community structure; however, less is known about their role on belowground seed banks. Understanding the influence of environmental filters on the composition of seed banks can reveal community dynamics across known environmental gradients and facilitate restoration efforts. We examined the influence of environmental filters on seed banks of vernal pools by characterizing seed density and diversity along seasonal inundation gradients. We also sampled seed banks from both naturally occurring and restored vernal pools that differed in their aboveground communities (invasive or native species dominated) in a long-term field study in Solano Co., California, USA. We found that the highest seed densities were associated with the longest inundation period and in the naturally occurring pools. Inundation gradients within a pool had little influence on seed bank diversity, yet among the pool types diversity and community metrics varied. The naturally occurring pools, regardless of invasion status, displayed a greater species richness and diversity than constructed pools. Our greenhouse germination trials did not show a strong relationship of inundation depths influencing species and total germination. Overall, we found that local position in the field along inundation gradients within a pool strongly affected soil seed bank density, while seed bank diversity varied more across pool types. Environmental filters may be limiting germination with the pool bottoms having the highest inundation and maintain the densest seed bank, but our lack of difference in the germination trials suggests alternative mechanisms other than inundation may be hindering germination.

Evaluating human-disturbed habitats for recovery planning of endangered plants

The recovery potential of endangered species is limited by the high prevalence of human-modified habitats, while effective in situ conservation strategies to identify and restore disturbed habitat within species ranges are lacking. Our goal was to determine the impact of human disturbance on the endangered endemic Barrens willow (Salix jejuna) to provide science-based protocols for future restoration of disturbed habitats; a key component of conservation and recovery plans for many rare plant species. Our study examined differences in substrate (e.g., % total plant cover, % species cover, substrate type) and vegetation in naturally- (via frost activity) vs human-disturbed limestone barrens (Newfoundland, Canada), across the entire species range of the endangered Barrens willow. There were distinct differences in substrate conditions and vegetation community structure between naturally- and human-disturbed limestone barrens habitat throughout the narrow range of this endemic willow. Human-disturbed sites are more homogeneous and differ significantly from the naturally-disturbed sites having a much coarser substrate (30% more gravel) with less fine grained sands, less exposed bedrock, decreased soil moisture, increased nitrogen content, and reduced phosphorus content. Substrate differences can inhibit return to the natural freeze-thaw disturbance regime of the limestone barrens, negatively affecting long-term persistence of this, and other rare plants. The structure of associated vegetation (specifically woody species presence) negatively affected willow abundance but was not linked to disturbance type. Human-disturbed sites are potential candidates for endangered plant recovery habitat if natural ecosystem processes, vegetation community structure, and habitat heterogeneity are restored, thereby supporting the establishment of long term viable populations.