Soil-vegetation Relationships Research Articles

Study of the soil-vegetation relationships of some chamaephytes in the southern landscape of Tlemcen (Oranie, Western Algeria)

Study of the soil-vegetation relationships of some chamaephytes in the southern landscape of Tlemcen (Oranie, Western Algeria)

Microclimate heterogeneity modulates fine-scale edaphic and vegetation patterns on the Himalayan treelines: Implications under climate change

In an era of global environmental change, the treeline shift triggered by recent climate warming has been reported worldwide. However, it is still unknown how site-specific microclimatic conditions regulate the soil-vegetation relationship at treelines, which constrains our capacity to down-scale broad global trends in the treeline shift at regional scale. In this study, we aimed to unravel fine-scale edaphic and vegetation patterns at two treeline sites in Kashmir Himalaya with in situ-measured microclimate using mini-loggers. At each site, we conducted sampling at the treeline leading edge, 100 and 300 m downslope and upslope. We employed boosted regression trees to find best predictors of the treeline vegetation among the microclimate and edaphic factors. We found intermediate microclimatic conditions at the leading edge but contrasting microclimates at the downslope and upslope. Our results demonstrate that the heterogeneity in microclimate driven by elevation strongly modulates the microsite edaphic conditions at the treelines, which in turn determines the fine-scale vegetation patterns. The soil temperature, moisture, pH, Cu, Zn, electrical conductivity and N were the best predictors of vegetation patterns at the treelines. The length of growing season measured at the treelines matched with the predicted values for the Himalaya, but growing season mean soil temperature of 7.31 – 8.15 °C recorded at the treelines is slightly higher than the postulated 6.4 °C global treeline isotherm. Our findings reveal that the soil microclimate strongly modulates edaphic and vegetation patterns at the treelines, thereby implying that even minor change in microclimate, like ongoing climate warming, can shift the current treeline position. However, this may be partially offset by the higher temperature isotherm in Kashmir Himalaya, thereby suggesting a slow-paced future treeline shift. Overall, the study advances our understanding about the crucial role of microclimate in determining soil-vegetation relationships at treelines with wide implications under ongoing and projected climate change.

Spatial Coupling Characteristics and Factors Influencing Soil–Vegetation Relationships in the Lower Part of the Shiyang River Basin

The relationship between soil and vegetation is an essential scientific issue in surface environment change. (1) Background: Since the implementation of the Shiyang River Basin governance plan, it has become necessary to quantitatively evaluate the impact of ecological restoration on soil–vegetation spatial coupling. (2) Methods: A coupled model and a coupled coordination model are adopted in order to investigate the spatial coupling characteristics of soil–vegetation systems. Additionally, we explore the influences of climate factors and soil properties on the level of spatial coupling and coordination. (3) Results: From 2015 to 2020, the soil–vegetation spatial coupling coordination in the lower reaches of the Shiyang River Basin was poor, and the average annual proportion of areas with medium and low degrees of uncoordination reached 79.3%. The level of spatial coupling coordination is differed under different vegetation coverage scenarios, and the bare land mainly showed low and moderate imbalances, accounting for 90.3% of the annual average area. The annual average proportions of short coverage and canopy coverage coordinated areas were 53.4% and 49.3%, respectively. In particular, vegetation in the Minqin hinterland is highly sensitive to environmental changes. With the implementation of ecological water conveyance, the spatial coupling coordination between soil and vegetation has improved slightly; however, the effect is not obvious. (4) Conclusions: Precipitation, temperature, and potential evaporation affect the level of coupling coordination between soil and vegetation, with the former having a positive effect and the latter two having negative effects. In addition, soil enriched with sulfate and sand contributed to the disharmony of soil–vegetation relationships in the study area.

Short-term land degradation driven by livestock grazing does not affect soil properties in semiarid steppe rangelands

The soil–vegetation relationships are reciprocal and fundamental for terrestrial ecosystem integrity. However, the long-term degradation of vegetation cover alters edaphic conditions, which can lead to degradation of habitats, and obstructs proper ecosystem functioning. This study aimed to assess the effects of the degradation of perennial steppe vegetation due to overgrazing (i.e., continuous and free grazing) on the physicochemical characteristics and soil fertility in the steppe rangelands of Halfa (Macrochloa tenacissima syn. Stipa tenacissima) of semi-arid areas in Algeria. The edaphic parameters of the superficial horizons of degraded steppes and other undegraded steppes were compared in order to suggest adequate strategies for rangeland management and remedy the degradation of vegetation and thereby ensure the sustainability of these agro-pastoral systems. The soil, collected from the surface horizons (A1 and A2) of pedological profiles, was analyzed according to standard methods of soil physicochemical analyses to determine the particle size fractions (clay, silt, and sands), pH, electrical conductivity (EC), total and active CaCO3, organic matter (SOM), organic carbon, total nitrogen, and the C:N ratio. The distribution and variation of soil parameters between horizons and the two types of steppes were examined using generalized linear mixed models and redundancy analysis. Findings of this study revealed that the degradation of steppe vegetation cover by short-term overgrazing did not cause a significant variability in soil physicochemical parameters between degraded and undegraded steppes and the horizons A1 and A2. The sites studied have clayey–silty textures in non-degraded steppes and coarse textures dominated by sands in degraded steppes. The edaphic environment of the Halfa grass steppes was characterized by a calcareous substratum with high carbonate content (total CaCO3 = 36.8–41%, active CaCO3 = 17.5–18.5%), with an alkaline pH (8.09–8.19) and EC averaging 0.99 ± 1.24 dS/m. Soils had low SOM contents (1.42–2.93%), organic carbon (0.82–1.64%), and nitrogen (0.1–0.15%). The strong positive correlations recorded between the fine-size fractions, SOM, total CaCO3, nitrogen, and EC indicated good soil structural stability in undegraded steppes, while the negative correlations between these same variables with sand and pH substantiate the structural degradation of the soil. The negative correlation between C:N ratio and SOM indicated that the rate of SOM mineralization was rapid in semiarid steppes, with a higher fertility state in the undegraded steppe. Our findings suggest and urge to implement a restoration plan against the degradation of semi-arid Halfa steppes in order to avoid the irreversible state of soil and habitat destruction in the future because even the degradation of rangeland plant cover due to livestock overgrazing—in the short term—has not affected the edaphic characteristics of steppe rangelands.

Impacts of Nicotiana glauca Graham Invasion on the Vegetation Composition and Soil: A Case Study of Taif, Western Saudi Arabia.

Invasive species are considered a serious problem in different ecosystems worldwide. They can compete and interfere with native plants, leading to a shift in community assembly and ecosystem function. The present study aimed to evaluate the effects of Nicotiana glauca Graham invasion on native vegetation composition and soil of the most invaded locations in the Taif region, Western Saudi Arabia, including Alwaht (WHT), Ar-Ruddaf (RDF), and Ash-shafa (SHFA). Plant species list, life span, life form, and chorotypes were assessed. Six locations highly infested with N. glauca shrubs were selected, and the morphological parameters of the shrubs were measured. Within each location, richness, evenness, relative density of species, and soil were measured either under the canopy of N. glauca shrubs or outside the canopy. Floristic analysis revealed the existence of 144 plant species, mainly perennial. The shrubs at the SHFA1 location showed the highest values of all measured morphological parameters. The WHT 1 location showed high richness and evenness, while the WHAT 2 location showed less richness and evenness. The invaded locations showed substantial variation in the community composition. Additionally, the effect of N. glauca on the understory species varied from competition to facilitation, where most of the understory species were inhibited. As an average of all locations, 65.86% of the plant species were recorded only outside the canopy of N. glauca. The vegetation analysis revealed that the SHFA location is more vulnerable to invasion that could be ascribed to its wide range of habitats and high disturbance. The soil–vegetation relationships showed significant variations among the studied locations regarding soil composition, and thereby showed a wide ecological range of the invasive shrubs N. glauca. Therefore, the invasion of N. glauca in the Taif region altered the species interactions, nutrients, and soil properties.

Do Anthropogenic Activities Affect Floristic Diversity and Vegetation Structure More Than Natural Soil Properties in Hyper-Arid Desert Environments?

Egypt is characterized by its hyper-arid desert environment with high temperature, scanty rainfall, high evapotranspiration rate, and patchy scattered precipitation-dependent vegetation. Located in this peculiar ecosystem, the northeastern part of the eastern desert occupies vast areas where this study was conducted. Despite some protection in this area, destruction of plant cover, soil erosion, and degradation of natural habitat are still occurring. Among the complex array of anthropogenic disturbances that directly affect species diversity, over-grazing, road construction, over-collection of plants, salinization, over-cutting, military activities, urbanization, and industrialization were encountered. The aim of this study was to assess the effect on long-lasting anthropopressure on the current floristic and ecological status of the unprotected area in comparison to the protected one. Two areas were chosen for detailed studies: protected (Wadi Degla; WD) and unprotected (Cairo-Suez road, SR). Fourteen soil variables were used to assess the soil–vegetation relationships in the two areas. An assessment of seven human activities (over-grazing, over-collection, introduced species, land degradation, urbanization, solid wastes, and military activities) was carried out at four levels of disturbance intensities. A floristic presence/absence data set of 25 plots × 56 species, including 14 plots for SR and 11 plots for WD, was employed in the analyses. The application of multivariate analysis techniques such as cluster analysis (for classification), indicator species analysis (ISA) and the multi-response permutation procedure (MRPP), canonical correspondence analysis (CCA), and redundancy analysis (RDA) for ordination were performed in the data analysis. Generally, a total of 85 plant species belonging to 68 genera and 30 families was recorded. Asteraceae, Chenopodiaceae, Fabaceae, Zygophyllaceae, Poaceae, Brassicaceae, and Geraniaceae were the largest families, constituting more than 50% of the total flora. Chamaephytes, therophytes, hemicryptophytes, and phanerophytes prevail in the life form spectrum. Chorological analysis showed that the Saharo-Arabian element, whether pure or combined with other chorotypes, dominated the current flora, whereas the Mediterranean chorotype was very poorly represented. Application of cluster analysis yielded eight vegetation groups: I–IV for the Cairo-Suez road, and V–VIII for Wadi Degla. This study indicated the disappearance of several plant communities that were previously of common occurrence such as Retama raetam, Anabasis articulata, Ephedra alata, Artemisia monosperma, Zygophyllum decumbens, Lasiurus hirsutus, and Panicum turgidum. Partial CCA (pCCA) for the unprotected area revealed that most of the variance (45.7%) was attributed to the anthropogenic variables more than soil factors (14.5%). Like what was revealed in other unprotected areas, a clear relationship between anthropogenic pressure and habitat fragmentation was observed. Long-term, intensive human activities caused vegetation degradation, species loss, and a decline in plant richness. Hence, the highest species richness value was recorded in the protected area. Over-grazing, land degradation, and military activities were not correlated with the diversity indices, whereas over-collection of plant species, urbanization, and solid wastes were significantly negatively correlated with both α-diversity and the Shannon–Wiener index. Suitable protection measures should be taken to reduce the anthropogenic pressures in this ecosystem as well as some conservation programs and management plans should be implemented to save biodiversity.

Soil-vegetation relationships in Mediterranean forests after fire

BackgroundWildfires are one of the major environmental concerns in Mediterranean ecosystems. Thus, many studies have addressed wildfire impacts on soil and vegetation in Mediterranean forests, but the linkages between these ecosystem compartments after fire are not well understood. The aim of this work is to analyze soil-vegetation relationships in Mediterranean burned forests as well as the consistency of these relationships among forests with different environmental conditions, at different times after fire, and among vegetation with different functional traits.ResultsOur results indicate that study site conditions play an important role in mediating soil-vegetation relationships. Likewise, we found that the nature of soil-vegetation relationships may vary over time as fire effects are less dominant in both ecosystem compartments. Despite this, we detected several common soil-vegetation relationships among study sites and times after fire. For instance, our results revealed that available P content and stoichiometry (C:P and N:P) were closely linked to vegetation growth, and particularly to the growth of trees. We found that enzymatic activities and microbial biomass were inversely related to vegetation growth rates, whereas the specific activities of soil enzymes were higher in the areas with more vegetation height and cover. Likewise, our results suggest that resprouters may influence soil properties more than seeders, the growth of seeders being more dependent on soil status.ConclusionsWe provide pioneer insights into how vegetation is influenced by soil, and vice-versa, in Mediterranean burned areas. Our results reflect variability in soil-vegetation relationships among study sites and time after fire, but consistent patterns between soil properties and vegetation were also detected. Our research is highly relevant to advance in forest science and could be useful to achieve efficient post-fire management.

Soil-vegetation relationships and community structure in a "terra-firme"-white-sand vegetation gradient in Viruá National Park, northern Amazon, Brazil

Viruá National Park encompasses a vast and complex system of hydromorphic sandy soils covered largely by the white sand vegetation ("Campinarana") ecosystem. The purpose of this study was to investigate a vegetation gradient of "terra-firme"-white sand vegetation at the Viruá National Park. Nine plots representing three physiognomic units were installed for floristic and phytosociological surveys as well as to collect composite soil samples. The data were subjected to assessments of floristic diversity and similarity, phytosociological parameters and to statistical analyses, focused on principal components (PC) and canonical correspondence analysis (CCA). The vegetation of the Campinaranas types and Forest differed in biomass and species density. Ten species, endemic to Brazil, were particularly well-represented. PC and CCA indicated a clear distinction between the studied plots, based on measured soil variables, especially base sum and clay, which were the most differentiating properties between Campinarana and Forest; For the separation of the Campinarana types, the main distinguishing variable was organic matter content and cation exchange capacity. Higher similarity of Campinaranas was associated to a monodominant species and the lower similarity of Forest was related to the high occurrence of locally rare species.

Primary vegetation succession and the serpentine syndrome: the proglacial area of the Verra Grande glacier, North-Western Italian Alps

Initial stages of pedogenesis are particularly slow on serpentinite. This implies a slow accumulation of available nutrients and leaching of phytotoxic elements. Thus, a particularly slow plant primary succession should be observed on serpentinitic proglacial areas. The observation of soil-vegetation relationships in such environments should give important information on the development of the “serpentine syndrome”. Plant-soil relationships have been statistically analysed, comparing morainic environments on pure serpentinite and serpentinite with small sialic inclusions in the North-western Italian Alps. Pure serpentinite supported strikingly different plant communities in comparison with the sites where the serpentinitic till was enriched by small quantities of sialic rocks. While on the former materials almost no change in plant species composition was observed in 190 years, 4 different species associations were developed with time on the other. Plant cover and biodiversity were much lower on pure serpentinite as well. Extremely low P and high Ni contents in soil were strongly related with these differences, but none of them could be interpreted as the actual limiting factor for plant development on pure serpentinite. Other nutrients or bases were not related with the different primary succession speed and species composition.

Hummocks affect soil properties and soil-vegetation relationships in a subalpine grassland (North-Western Italian Alps)

Earth hummocks are small cryogenic mounds, covered by grass, closely spaced in grassland or wetlands. Hummock microtopography establishes specific microclimatic conditions, with small-scale variations in soil thermal properties and water regimes, which influence biogeochemical cycles. These properties, coupled with different litter decomposability, may cause variations on soil physical and chemical properties and pedogenesis, as well as a selective distribution of plant species.The work has been carried out at the LTER site of Tellinod (Torgnon, Aosta Valley, NW, Italy). The site is characterized by a Nardus stricta subalpine hummocky grassland located at 2100masl, which shows the dominance of Nardus on hummocks and a prevalence of dicotyledons in interhummocks (i.e. the depressions between consecutive hummocks). Such distribution indicates that earth hummock pattern was reflected in soil properties. In order to confirm this hypothesis, we analyzed and compared soil pedogenesis and topsoil characteristics between hummocks and interhummocks. In addition, litter bags were incubated in hummock and interhummock positions to investigate litter decomposition rate as related to microtopography and plant species and its effects on topsoil edaphic properties.The results confirm that hummocky topography significantly influences topsoil properties, pedogenesis and vegetation distribution, with large differences between hummocks and interhummocks. The hummocky soil can be fully classified as Podzol, based on both the morphological and chemical diagnostic properties; however, morphological and chemical evidences indicate that the degree of podzolization differs significantly under hummocks and interhummocks. In addition, the results verify a faster decomposition of dicotyledons in the nutrient-richer interhummock topsoils compared to the podzolized hummocks positions, and an overall slower decomposition rate of Nardus litter. All these factors contribute to the creation and conservation of a unique pedo-environment in this subalpine grassland.

Soil-vegetation relationships on a banded ironstone 'island', Carajás Plateau, Brazilian Eastern Amazonia.

Vegetation and soil properties of an iron-rich canga (laterite) island on the largest outcrop of banded-iron formation in Serra de Carajás (eastern Amazonia, Brazil) were studied along a topographic gradient (738-762 m asl), and analyzed to test the hypothesis that soil chemical and physical attributes play a key role in the structure and floristic composition of these plant communities. Soil and vegetation were sampled in eight replicate plots within each of the four vegetation types. Surface (0-10 cm) soil samples from each plot were analyzed for basic cations, N, P and plant species density for all species was recorded. CCA ordination analysis showed a strong separation between forest and non-forest sites on the first axis, and between herbaceous and shrubby campo rupestre on the second axis. The four vegetation types shared few plant species, which was attributed to their distinctive soil environments and filtering of their constituent species by chemical, physical and hydrological constraints. Thus, we can infer that Edaphic (pedological) factors are crucial in explaining the types and distributions of campo rupestre vegetation associated with ferruginous ironstone uplands (Canga) in Carajás, eastern Amazonia, therefore the soil properties are the main drivers of vegetation composition and structure on these ironstone islands.

Impacts of trails on plants, soil and their interactions in the subalpine meadows of Mount Jade Dragon, Northwestern Yunnan of China

Trails are a type of tourism infrastructure that impact vegetation and soil, which are essential for sustainable recreation practices. There is limited recreation ecology research on the impact of trails in China, especially on Mount Jade Dragon, where it is characterized as a global biodiversity hotspot with high scenic value. Impacts of trails on vegetation, soil and their interaction were assessed for the subalpine meadow area of Mount Jade Dragon. The aims of this research were: (i) to assess trail effects on vegetation, soil and their interaction, and (ii) to evaluate the effects of the trail type and usage level on trail impacts. Vegetation and soil properties were measured at control and trailside sites along formal and informal trails of different usage levels. A three-way analysis of variance was performed to determine the effects of site location, trail type and usage level. Canonical correspondence analysis was used to visualize species composition along trails and to ordinate species with respect to the soil variables. A multiple linear regression model was used to examine relationships between soil variables and vegetation cover. The results showed that trails led to vegetation cover, height and species richness reduction as well as soil organic matter and moisture content loss. Trails also affected soil-vegetation relationships. Soil organic matter and soil moisture content played an important role in determining vegetation along trails at low-usage sites. The soil-vegetation relationships were weakened at high-usage sites. Compared with informal trails, formal trails had a protective effect on vegetation cover, especially at high-usage sites. These results suggest that park managers should limit the spread of informal trails at high-usage sites, upgrade existing informal trails, and rehabilitate damaged areas. Further, greater recognition should be given to research on soil protection and soil-vegetation relationships.

Small-scale variability of soil properties and soil–vegetation relationships in patterned ground on different lithologies (NW Italian Alps)

Cryogenic patterned ground represents spectacular periglacial landscapes. On the Alps, sorted/nonsorted patterned ground features larger than 1m, formed by deep seasonal cryoturbation with or without permafrost, occupy exposed, stable surfaces at high altitudes and represent a particularly harsh habitat for plant life.We analyzed soils across transects through typical active patterned ground features (sorted/nonsorted circles and stripes) on four common lithotypes (calcschists, serpentinite, gabbros and gneiss) in the Western Italian Alps, in order to observe the small-scale lateral and depth variability in physico-chemical properties, and their association with cryoturbation, plant cover and species distribution.Cryoturbation was correlated with lateral/vertical textural sorting across features, mostly visible on silt and coarse sand, but with opposite trends on sorted and nonsorted patterned ground types. A strong lateral variability in organic carbon was detected, with high values near the better vegetated rims and low contents in the centers. Exchangeable bases, heavy metals and nutrients followed the same distribution. However, the differences inherited from the parent materials were overwhelming.Climate is the main driver of high altitude ecosystems, reducing total plant cover and causing cryoturbation, which in turn creates strong edaphic gradients over small distances. Plant species and communities are well correlated with edaphic properties inherited from the parent materials, such as exchangeable Ca and heavy metals.

Spatial heterogeneity of soil and vegetation characteristics and soil-vegetation relationships along an ecotone in Southern Mu Us Sandy Land, China

This study aims to examine the changes in the spatial heterogeneity of soil properties at different soil layers, the spatial heterogeneity of soil and vegetation characteristics along an ecotone, and soil-vegetation relationships along the ecotone in a critical area of desertification. A study site was established across a Lespedeza potaninii (dominant) community (LPC) and an Artemisia ordosica (dominant) community (AOC), with the ecotone between these two communities. In this study, “along the ecotone” means from LPC, via the ecotone, and then to AOC. Three parallel transects (300-m long) were arranged at 50-m intervals along the site. Along each transect, at 10-m spacings, 1 m × 1-m quadrats were marked for the vegetation survey and soil sampling. Soil samples were analyzed in the laboratory after natural air-drying. Data analyses were conducted with a combination of classical and geostatistical methods. In most cases, species importance values and soil properties changed significantly (P < 0.05) along the ecotone. Most soil and vegetation variables were moderately spatially autocorrelated. Kriging interpolated maps showed patch patterns of soil chemical properties. The C/(Co + C) values of soil properties were larger at 5–10-cm than those at 0–5-cm. Vegetation characteristics were mainly positively correlated with soil organic carbon (SOC), total nitrogen (TN), and electrical conductivity (EC). TN at 0–5-cm (TN1), EC at 0–5-cm (EC1), and available potassium at 5–10-cm (AK2) were selected as the predictors for plant species richness and diversity in the stepwise regression analysis between vegetation characteristics and soil properties. Soil nutrients decreased significantly (P < 0.05) along the ecotone. Soil and vegetation properties had moderate spatial heterogeneity. Soil properties had a stronger spatial heterogeneity at subsurface layers compared to surface layers. TN1, EC1, and AK2 were the predominant factors for the plant community structure along the ecotone in the critical area of desertification.

Podzolized soils and paleoenvironmental implications of white-sand vegetation (Campinarana) in the Viruá National Park, Brazil

The vast and complex system of hydromorphic sandy soils in northern Brazilian Amazonia remains little studied. We investigated the broader soil–vegetation relationships in white-sand areas under Campinarana vegetation in the Viruá National Park, discussing pedogenetic processes as well as some paleoenvironmental implications. Our hypothesis was that white-sand areas were not covered with savanna grassland during dryer periods, and remained under arboreal vegetation. Seven soil profiles were studied along a typical forest–shrub–grassland gradient. All soils are acid, depleted in bases, with a fine-sandy texture. The vegetation gradient is associated with decreasing soil organic carbon contents. Imogolite is present in some soils as indicated by selective dissolution and microchemical analyses. Podzolization, indicated by illuvial organic and Al-rich coatings on quartz grains is clearly observed in thin sections. The mineralogy of the clay fraction indicates the occurrence of residual kaolinite, hydroxy-interlayered 2:1 mineral and traces of gibbsite, from alteration of sedimentary parent material. Carbon isotope analysis suggests a predominance of arboreal-shrubby vegetation (C3-type) during past drier periods of the Late Quaternary. We conclude that the local distribution of vegetation is primarily associated with edaphic factors. Poor drainage, impermeable subsurface layers, very sandy soils and intense leaching created subtle but contrasting pedo-environments, closely related to vegetation types. Overall, these Amazon Spodosols and Podzol-like soils are associated with C3-plant-dominated vegetation.

Irrigation with seawater as a strategy for the environmental management of abandoned solar saltworks: A case-study in SE Spain based on soil–vegetation relationships

Groundwater withdrawal by desalination plants might lead to a drop of the piezometric levels of aquifers, causing negative impacts, especially in water-dependent ecosystems. Management strategies are necessary to overcome these potential problems, particularly in abandoned solar saltworks—wetlands which are particularly prone to degradation by desiccation. This paper reports the soil–vegetation relationships in one of these wetlands (Agua Amarga salt marsh, SE Spain), in which a pioneer programme of irrigation with seawater is applied to correct the environmental impacts of two desalination plants. Depth of water level and soil Eh, bulk density, moisture and salinity were determined in December 2011 and June and October 2012, in 63 plots from 12 different environments/types of vegetation. Multivariate analyses were used to identify gradients, and a model of soil–vegetation relationships was elaborated to contribute to the management of the marsh. Two different situations were identified: the periphery (drier and less saline soils) and the abandoned saline ponds (wetter and more saline soils). The three environments/types of vegetation of the periphery (Suaeda vera, Lygeum spartum and Limonium spp. stands) were separated according to the seasonal behaviour of soil salinity and moisture, regardless of the irrigation programme. Hence, modifications in the vegetation distribution should be mainly attributable to environmental factors, including possible consequences of climate change. The nine environments/types of vegetation of the abandoned saline ponds (Sarcocornia fruticosa, Arthrocnemum macrostachyum growing in patches with and without the presence of seedlings, bare soils among A. macrostachyum patches, mixed stands with S. fruticosa and A. macrostachyum, Salicornia patula, flooded ponds with Ruppia maritima, Phragmites australis and a burned zone) were separated mainly according to soil moisture, water level in the soil profile, Eh and salinity. In this zone, vegetation can be used as a bioindicator to detect the consequences of the irrigation programme, which should be carefully managed if biodiversity and habitat variety have to be preserved. Our results indicate that the amount of seawater pumped is a critical issue and must be planned taking into account not only the vegetation but also the current soil properties such as bulk density (that influences water infiltration and retention) and salinity (mainly determined by the salts that remain in the soils due to the former use of the ponds as solar saltworks).

Soil-Vegetation Relationships of Saline Wetlands in North East of Algerian Sahara

In this study, we conducted an ecological analysis of three saline wetlands in the region of Ouargla, which is located in north east of the Algerian Sahara, in order to understand the environmental factors controlling plant distribution. This study was based upon the quantitative analysis of vegetation and soil samples by the quadrat method. A total of 12 transects were investigated, and the parameters of vegetation such as density, cover, and Jaccard index as well as soil characteristics (electrical conductivity, moisture, and pH) were evaluated. Nine perennial species belonging to seven families were identified in the three studied habitats. Results of the Principal Component Analyses (PCA) showed that community structure and distributional pattern of species were mainly dependent on the salinity and moisture gradient. Halocnemum strobilaceum was observed to grow in highly salt-affected soils, thus being the most salt tolerant species. Phragmites communis was distributed widely in the study area. Aeluropus littoralis was detected throughout transects and was significantly correlated with soil salinity. Juncus maritimus, Sonchus maritimus, and Cynodon dactylon occupied mainly the wettest soils. Tamarix gallica was irregularly distributed in all the salt-affected habitats. Zygophyllum album was located in the outermost belt of vegetation, whereas Mollugo nudicaulis was observed only in the least salt-affected soils.

Soil-vegetation relationships on a cobbly limestone floodplain. Anticosti Island, Quebec

The limestone floodplain of the Galiote River. Anticosti Island (Quebec) is occupied by 4 shrub associations: &lt;em&gt;Dryadetum drummondi&lt;/em&gt; (37%). &lt;em&gt;Juniperetum horizontalis&lt;/em&gt; (15%). &lt;em&gt;Dryadetum integrifolae&lt;/em&gt; (4%) and &lt;em&gt;Potentilletum fruticusae&lt;/em&gt; (3%) as well as by 6 less Important communities. primarily herbaceous. Four new subassociations are presented: &lt;em&gt;D. d. dryadetosum drummondii. D. d. danthonietosum spicatae, D. i. juniperetosum horizontalis&lt;/em&gt; and &lt;em&gt;J. h. dryadetosum integrifoliae&lt;/em&gt;. The vegetation colonizes soil representative of the Regosolic. Brunisolic and Gleysolic orders, composed of calcareous material at pH greater than 7 with a base saturation capacity of more than 100%. These soils are first colonized by pioneer plants such as Dryas. which stabilize the substrate thus facilitating the establishment of a less specialized vegetation and leading finally to forest development. This succession follows a topographical gradient that runs from the river to the forest; the river being the principle element determining the distribution of the described plant communities.

Species Richness, Community Specialization and Soil-Vegetation Relationships of Managed Grasslands in a Geologically Heterogeneous Landscape

The increasing importance of the conservation value of managed grasslands has led to many studies exploring edaphic determinants of grassland biodiversity. Most studies, however, come either from very large areas, where biogeographical factors such as dispersal limitation may play a role, or from small, but ecologically rather uniform, regions. In addition, few studies further distinguish between plant specialists and generalists in the interpretation of the observed patterns. Here we studied species richness in semi-natural, managed grasslands in the Stražovske vrchy Mountains in the West Carpathians, Slovakia, where there is a matrix of different bedrocks (crystalline, sandstone, claystone, limestone) on a steep altitudinal gradient. In 89 vegetation plots we sampled the species composition of vascular plants and bryophytes and measured soil chemistry, slope angle, heat index, altitude and soil depth. We further applied Ellenberg indicator values and classified species into community specialists or generalists based on the analysis of a large phytosociological database. Using cluster analysis, we delimited five vegetation types that clearly differed in response to soil characteristics. Species richness varied between 19 and 64 species per 16 m2. The main compositional gradient correlated with measured soil pH and calcium, but species richness was not significantly correlated with these factors. Soil available phosphorus was not associated with species composition as has been found elsewhere, but it did correlate negatively with species richness and the richness of specialists. Overall, species richness was largely driven by the number of specialists in the plot and particular vegetation types differed conspicuously in their number. We further found significant effects of iron, potassium and sodium on species richness, species composition and the representation of specialists and generalists. Our results provide new insights into the determinants of diversity in managed grasslands as well as to the theoretical species pool concept, explaining species richness variation along a pH gradient.

THE APPLICATION OF SOIL SCIENCE TO FORESTRY IN LAND USE PLANNING AND WATERSHED MANAGEMENT IN SRI LANKA.

Allocation of land to forestry in Sri Lanka has hitherto been based an "adhoc" considerations. The over-riding approach has been to allocate the least productive soils to various forms of forestry. Furthermore, even current recommendations of forest species for forestry plantations are made mainly on the basis of climate or geographic region with no recognition given to the occurrence of different kinds of soils within a particular region.Some very striking and significant soil-vegetation relationships have been observed and described, especially in the dry and intermediate zones of this country by several field scientists and researchers engaged in the Soil Survey of Sri Lanka since the early nineteen sixties. In several recorded instances it has been observed that the nature of soil exerts a profound influence on the growth and performance of some species that make up the 'dry-mixed-evergreen" forest. Some relevant examples are cited and further discussed.Soil related factors should, therefore, be considered as having a very important bearing on species performance and forest productivity on different kinds of soils occurring within the same agro-ecological region. Meaningful land use planning for forestry should, therefore, be based on a proper understanding of the soil-vegetation relationships. Supporting examples are cited and discussed. An argument is also made for allocating land with better quality soils for commercial forestry plantations.A proper recognition of the soil water-vegetation-evaporation balance in different environments is considered the key to understanding the role of forests in watershed management both in the dry and the wet zones of this country. Based on studies conducted by the Land Water Use Division of the Department of Agriculture over the last two decades, the selective role of a forest cover in the different environments (dry and wet) of the country are discussed in relation to watershed management.