Re-establishment Of Vegetation Research Articles

Protection of Metasequoia glyptostroboides Hu et Cheng in China

Metasequoia (Metasequoia glyptostroboides Hu et Cheng) is an important but endangered tree species. In a sense, the course of protection of the metasequoia can be considered a miniature of the history of the protection of rare Chinese plants over the past 50 years. The approval and establishment of the National Class Nature Reserve for metasequoia is a milestone in this course. A thorough understanding of this course is beneficial to design the correct future protection plans and for taking effective measures. In this paper the entire protection course of metasequoia is reviewed, three detailed measures are proposed according to the present situation and existing problems and discussed as follows. 1) We should reinforce unceasingly the establishment of National Nature Reserves of metasequoia, put emphasis on the protection of the original natural mother trees (ONMTs) of metasequoia, design farsighted projects to protect the ONMTs and strictly implement and enforce the regulations or laws regarding the protection of metasequoia. The establishment and functions of the organization should meet the demands of protecting the ONMTs and developing metasequoias. The budget should support and the quality of the personnel assigned to this task should satisfy the protection and development of the ONMTs. We should also promote the complete protection of the ONMTs at the same time and strengthen the protection and restoration of the ONMTs and their ecosystem in the Xiaohe valley, Lichuan County, Hubei Province, one of the natural concentration areas of ONMTs in the world. 2) A gene bank should be established for comprehensive protection of the genes of existing original mother trees of metasequoia. 3) The key is to study the theoretical fundamentals of restoration and re-establishment of natural vegetation of metasequoia in the Xiaohe valley to harmonize the relation among environmental departments, forestry sectors, academies of sciences and other educational or research units, to carry out scientific research and strengthen academic exchanges to promote jointly the protection and utilization of metasequoia and other natural resources in China.

Relationships of post-fire aeolian transport to soil and atmospheric conditions

Aeolian transport is an important contemporary geomorphic process in semiarid cold deserts; most evi- dent when vegetative cover is temporarily eliminated by wildfire. The erodibility of recently burned sur- faces is not stable in time, and near-surface moisture is expected to affect erodibility prior to regrowth of vegetation. In this study we examine effects of soil and atmospheric moisture on wind erodibility of loess soil following late-summer (2007) wildfire at the US Department of Energy, Idaho National Laboratory in southeastern Idaho, prior to re-emergence of vegetation. We measured threshold wind velocities, soil vol- umetric water content, air temperature, relative humidity, and vapor density at two sites with severe and moderate burn intensity, respectively, and an unburned site. Results indicate that erodibility, as mea- sured by threshold wind velocities, decreased with time following fire. Little sediment transport was detected at the unburned site and erodibility could therefore not be determined. Multiple regression models with predictors including soil water, atmospheric moisture, and time variables explained 83% and 69% of the variability in erodibility at the severe and moderate burn intensity sites, respectively. Erodibility decreased as soil volumetric water content increased to 15-20%, but was less responsive to further wetting. Erodibility predominantly decreased as atmospheric moisture increased, however, rela- tionships were complex. Multiple regression coefficients indicated erodibility increased as relative humidity increased at timescales of days-months. Positive and negative relationships were observed between erodibility and atmospheric moisture, within individual saltation events. Atmospheric and soil moisture appear important for post-fire wind erosion before re-establishment of vegetation.

Seed Reserves Diluted During Surface Soil Reclamation in Eastern Mojave Desert

Surface soil reclamation is used to increase the re-establishment of native vegetation following disturbance through preservation and eventual replacement of the indigenous seed reserves. Employed widely in the mining industry, soil reclamation has had variable success in re-establishing native vegetation in arid and semi-arid regions. We tested whether variable success could be due in part to a decrease of seed reserves during the reclamation process by measuring the change in abundance of germinable seed when surface soil was mechanically collected, stored in a soil pile for 4 months, and reapplied upon completion of a roadway. Overall seed reserve declines amounted to 86% of the original germinable seed in the soil. The greatest decrease in seed reserves occurred during soil collection (79% of original reserves), compared to the storage and reapplication stages. At nearby sites where stored surface soil had been reapplied, no perennial plant cover occurred from 0.5 to 5 years after application and < 1% cover after 7 years compared to 5% cover in nearby undisturbed areas. The reduction in abundance of germinable seed during reclamation was primarily due to dilution of seed reserves when deeper soil fractions without seed were mixed with the surface soil during collection. Unless more precise techniques of surface soil collection are utilized, soil reclamation alone as a means for preserving native seed reserves is a method ill-suited for revegetating disturbed soils with a shallow seed bank, such as those found in the Mojave Desert.

Do fungi have a role as soil stabilizers and remediators after forest fire?

The functional roles of fungi in recovery of forest ecosystems after fire remain poorly documented. We observed macrofungi soon after fire at two widely separated sites, one in the Pacific Northwest United States and the other in southeastern mainland Australia. The range of species on-site was compared against macrofungi reported after the volcanic eruption at Mount St. Helens, also in the Pacific Northwest. Each of the three sites shared species, particularly representatives of the genus Anthracobia. Soon after disturbance, we noted extensive mycelial mats and masses of fruit-bodies of this genus, particularly at heavily impacted microsites. The mycelial mats appeared to play an important functional role on-site, possibly aggregating soil particles in otherwise highly erodable landscapes. We hypothesise that fungi such as Anthracobia are pivotal species in early system recovery after disturbance, helping minimize the movement of soil in the absence of plant roots. As plant root systems recover, the importance of these fungi in soil stabilization may diminish. Other functional roles of early postfire fungi might include nutrient acquisition, leading to the reestablishment of vegetation. These potential roles need to be experimentally tested and relevant findings incorporated into programs aimed at restoring forest ecosystems after disturbance.

Sediment Fe:PO4 ratio as a diagnostic and prognostic tool for the restoration of macrophyte biodiversity in fen waters

Summary1. Globally, freshwater wetlands, including fen waters, are suffering from biodiversity loss due to eutrophication, water shortage and toxic substances, and to mitigate these pressures numerous restoration projects have been launched. Water quality data are generally used to evaluate the chances of reestablishment of aquatic vegetation in fen waters and shallow peat lakes. Here we investigated whether sediment characteristics, which are less prone to fluctuate in time, would result in more reliable predictions.2. To test if sediment characteristics can indeed be used not only for an easy and early diagnosis of nutrient availability and water quality changes in fen waters, but also for the prognosis of biodiversity response, we recorded the aquatic vegetation and collected surface water, sediment pore water and sediment samples in 145 fen waters in the Netherlands, Ireland and Poland.3. Endangered macrophyte species were more closely related to surface water chemistry than common species in terms of occurrence and abundance. Sites featuring endangered species appeared to have significantly lower turbidity and pH, and lower concentrations of SO4, PO4, total phosphorus (TP) and NH4 than other sites.4. PO4 and TP concentrations in the water layer increased markedly at PO4 concentrations above 5–10 μmol L−1 in the sediment pore water. High surface water PO4 and TP concentrations appeared to be SO4‐induced and only occurred below certain threshold values for pore water Fe:PO4 (3.5 mol mol−1) and total sediment Fe:P (10 mol mol−1).5. Interestingly, the occurrence of endangered species also correlated strongly with sediment and sediment pore water ratios; the number of endangered species increased markedly at pore water Fe:PO4 ratios above 1 mol mol−1, whereas their actual abundance had the greatest increase at ratios above 10 mol mol−1. Additionally, endangered species seemed to be more sensitive to accumulation of potentially toxic substances such as sulphide and ammonium than non‐endangered species.6. As an indicator of both biogeochemical processes and biodiversity, pore water Fe:PO4 ratios could be a valuable diagnostic and prognostic tool for the restoration of water quality and biodiversity in fen waters, e.g. for selecting the most promising sites for restoration and for optimization of restoration measures.

English

In watersheds of the mid-Atlantic region of the US where sulfide spoils occur from mining operations, geochemical reactions develop additional acids in the soil and water supply. The resulting condition lowers ambient pH to very low values (2 to 4 SU). The low pH impairs the soil chemistry and water quality to the extent that native flora and fauna can not survive on the site. This work presents the design and evaluation of remedial work implemented to abate acid mine drainage from a sulfide mine (Valzinco Mine) in the Piedmont Provence of Virginia, USA. Water quality conditions were measured before and after the remediation work, and documented the re-establishment and abundance of native wetland and aquatic vegetation within the site. Data showed that average pH increased from 3.4 to 5.1 and a decrease in total dissolved solids (Fe, Al, Zn, Pb, Cu, Cd, and SO4 2- ) over the study period. Initial wetland vegetation, both planted and volunteer, quickly colonized the site with an average ground cover of >74% after five years. Aquatic vegetation cover averaged >50% after 2 years and many plots had coverage >100%. Composition, species richness, and abundance of the new vegetation communities was similar to that of near-by reference (un-affected by mine activities) wetland (>75%, 6.0 spp. m -2 vs. 5.5 spp. m -2 , average cover 74% vs. 67%, respectively). Two amphibians (southern leopard frog, pickerel frog) and two aquatic reptiles (brown water snake and northern water snake) were captured on the site during the fifth year, indicating a return of herpatifauna to the wetland and aquatic communities. We conclude that the increase in pH, decline in total dissolved minerals, success of the re- vegetation of the site, and return of the reptiles to the site, is a strong indication that the remedial work successfully restored the soil and water chemistry closer to pre- mining conditions. Therefore, we suggest that the successful restoration of this site was based on sound hydrological and biogeochemical principles that can be applied to restoration efforts in other acid damaged watersheds in the mid-Atlantic region.

Sand-fixing effects of Caragana microphylla shrub in Horqin sandy land, North China

In the semi-arid Horqin sandy land of north China, Caragana microphylla, a leguminous shrub, is the dominant plant species and is widely used in vegetation reestablishment programs to stabilize shifting sand. The sand-fixing effects of 6-and 11-year-old C. microphylla plantations were studied. The results showed that: 1) the wind velocity and sand transport rate in the plantation were less than those in dunes; 2) the air temperature in the plantation was lower than those in dunes. Relative humidity was higher and the soil temperature was lower, which benefits plant growth; 3) the physical and chemical characteristics of soil were improved to some extent over age. The porosity and percentage of tiny sand (diameter 0.05–0.1 mm) and clay particle (diameter < 0.05 mm) increased, bulk density in surface soil decreased, and saturated water-holding capacity improved. Organic C, total N, available N and available K content increased gradually, and soil fertility was enhanced.

Soil properties and physiographic factors controlling the natural vegetation re-growth in a disturbed catchment of the Central Spanish Pyrenees

Large changes in land use have occurred in the Central Spanish Pyrenees during the twentieth century. This mountain area supported an intense human use since the Middle Ages, that greatly transformed the natural landscape. The land uses changed dramatically during the first half of the twentieth century, due to major socioeconomic forces which lead to depopulation and land abandonment. Since then, a process of natural vegetation recovery has taken place. The anthropogenic impact during centuries deteriorated the soil quality, threatening the sustainability of agroecosystems and the natural vegetation re-growth. In this study, a soil survey was performed to identify the soil types and the physico-chemical properties of the soil that are relevant for maintaining the soil function for the recovery of vegetation after land abandonment. The study was conducted in the Arnas River catchment, which is representative of the region. The highest cation exchange capacity (CEC), nutrients, water retention, water availability and infiltration rates, as well as the lowest pH and carbonates, occurred in Lithic Hapludolls and Calcic Haploxerolls at the shady aspect, under a forest cover. Lithic Ustochrepts and Lithic Xerorthents on the sunny aspect, which were covered by shrubs, were of lesser quality than were the deeper and better-developed soils on the shady aspect. This is seen as an evidence of different patterns of soil degradation, which conditioned the re-growth of natural vegetation after land abandonment. The results provide insights into the main soil factors that have affected the re-establishment of natural vegetation in recent years. Recommendations are given for designing effective strategies for soil conservation after land abandonment in similar mountain environments.

Restoring bare patches in the Nama-Karoo of South Africa

Often veld degrades to a point beyond which vegetation cover, plant density and species composition do not recover despite the removal of the grazing impact. In such cases restoration interventions become necessary to assist with the re-establishment of vegetation. The efficacy of different techniques for the restoration of bare patches in the Nama-Karoo was investigated. Five different treatments, namely tilling, seeding and brush packing, and combinations thereof, were tested on the farm Hillmore in the Beaufort West district. Sown-in species established significantly better in the tilling+seeding+brush packing treatment (TSB), with Chaetobromus dregeanus and Atriplex semibaccata the most successful species. Important grazing species from the surrounding vegetation also established successfully in the different treatments. The tillage treatments were the most effective, especially the TSB treatment, which had significantly higher plant density and species richness than the other treatments. The results show that bare patches in the Nama-Karoo can be successfully revegetated with tillage treatments providing for rapid recolonisation of plants in the short term (over two years), and the tillage and seeding plus brush packing providing similar plant densities in the medium term (after five years). The tillage treatments resulted in higher plant density and species richness than the other treatments in the short term, a result that persisted with regard to species richness but not plant density in the medium term.

Riparian hydroecology: A coupled model of the observed interactions between groundwater flow and meadow vegetation patterning

Stream incision is altering the hydroecology of riparian areas worldwide. In the Last Chance watershed in the northern Sierra Nevada, California, logging, overgrazing, and road/railroad construction have caused stream incision, which resulted in drainage of riparian meadow sediments and a succession from native wet meadow vegetation to sagebrush and dryland grasses. Restoration efforts have been initiated to reestablish the ecosystem function of these systems. Original field data including stream stage records, water table hydrographs, sediment hydraulic properties, topographic transects, and aerial imagery of vegetation patterning were used to develop a model of an archetype meadow. Hydrologic behavior was simulated with a finite element model of variably saturated groundwater flow. This model was coupled to an empirical, time‐dependent, vegetation threshold relationship between vegetation type and depth to the water table. This was a two‐way coupling requiring an iterative approach because water table depth is a determinant of vegetation type, yet the vegetation regime influences water table depth through evapotranspiration. The hydrology and vegetation patterns were analyzed under pristine, degraded (incised), and restored conditions. For the case of deep streambed incision, our hydroecological model predicts the observed shift from mesic (wetter) to xeric (drier) vegetation communities and reproduces their imaged longitudinal zonation. This patterning is explained as a response to groundwater drainage to the stream, which creates dry zones with xeric vegetation adjacent to the stream, while preserving sufficient moisture at the margins of the meadow to support holdout populations of mesic vegetation. The model further predicts the reestablishment of meadow vegetation when the incised channel is filled and a new shallow channel is restored. The coupling of a near‐surface hydrologic model to a vegetation response model may be used to design stream restoration projects by predicting vegetation patterning.

Promoting microbial immobilization of soil nitrogen during restoration of abandoned agricultural fields by organic additions

Application of organic materials to soils to enhance N immobilization into microbial biomass, thereby reducing inorganic N concentrations, was studied as a management option to accelerate the reestablishment of the native vegetation on abandoned arable fields on sandy soils the Kiskunsag National Park, Hungary. Sucrose and sawdust were used at three different topographic sites over 4 years. N availability and extractable inorganic N concentrations were significantly reduced in all sites. Soil microbial biomass C and microbial biomass N increased significantly following C additions, but the microbial C to microbial N ratio remained unaffected. It is concluded that the combined application of the rapidly utilized C source (sucrose) promoted N immobilization, whereas the addition of the slowly utilized C source (sawdust) maintained the elevated microbial biomass C and microbial biomass N in the field.

Rehabilitation of field tunnel erosion using techniques developed for construction with dispersive soils

Past repairs of field tunnel erosion using mechanical treatments (deep ripping, contour furrowing, contour ripping, etc.) and reestablishment of perennial vegetation have often failed, resulting in further tunnelling. Techniques to prevent ‘piping’ (tunnel erosion) in earth dams constructed using sodic clays have not been used in the repair of field tunnel erosion; however, these techniques have the potential to reduce recurrent failure. Installation of an optical fibre cable in a Grey Sodosol and Grey Dermosol at a site near Dunalley, Tasmania, in November 2001, resulted in the formation of a 380-m-long tunnel erosion system. Detailed site investigations and soil analysis in 2004 indicated that the tunnel erosion resulted from the consequences of inadequate compaction during the installation of the optical fibre cable, and secondary processes such as capture of surface and subsurface flow, dispersion of sodic clays, and translocation of dispersed clay platelets through the poorly compacted fill. Repair works consisted of excavating the entire length of the tunnel system, chemical amelioration with gypsum, compaction of repacked fill to reduce internal porosity, and installation of sand blocks to capture and remove water moving along the reinstalled cable. Inspections conducted 2 years after completion of the repair works indicated the site to be stable; however, it is acknowledged that this is too short an interval to adequately assess the long-term stability of repair works and techniques employed at the site. Due to the costs associated with the application of dam construction techniques, their use for the repair of field tunnel erosion is likely to only be justified where continued erosion poses a risk of damage to high value infrastructure.

Organization of dung beetle communities (Coleoptera, Scarabaeidae) in areas of vegetation re-establishment in Feira de Santana, Bahia, Brazil

The present work refers to the study of colonization of four vegetation physiognomies considered as succession stages by Scarabaeidae beetles in Feira de Santana, Brazil. The four environments present structures of 1) herbs, 2) herbs and bushes, 3) bushes, and 4) bushes and trees. The last one has similar vegetation elements to the original vegetation of the area (Caatinga, in transition with deciduous forest). Beetles’ richness was not statistically different in the three structurally simpler habitats, the composition, as well as the abundance structure of the communities of the four sites were very similar. Guild structure changed in number and proportion of specimens, with an increase in the number of tunnelers as the vegetation grew in complexity. The positive/negatives effects on the composition and beetles’s community structure were related to the interference with the dissemination of odor plumes or maintenance of sources of resources (vertebrates). The organization of the functional structure in the beetles’ community should be related to the time needed for the establishment of complex ecological connections.

English

Mining wastes comprised of heavy metals and arsenic and deposited along Silver Bow Creek downstream of Butte, Montana have posed a threat to human health and the environment for over 100 years. Under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), the State of Montana has undertaken the remediation of more than three million cubic meters of mine waste deposited along approximately 40 kilometers of Silver Bow Creek and its floodplain. During remediation, mine waste is excavated from the stream and floodplain and the waste is placed in a regional repository or a local repository constructed for the project. The stream and floodplain have been rebuilt to restore their natural functions and maintain streambank stability during vegetation reestablishment. This paper presents results of water quality monitoring on Silver Bow Creek. Surface water and groundwater quality have greatly improved in the remediated reaches compared to pre-remediation conditions although copper and zinc still frequently exceed aquatic life standards. Some water quality problems persist including the elevated nutrient levels originating at the Butte wastewater treatment works and the elevated copper and zinc concentrations in groundwater, which affect aquatic life in surface water systems.

A Leguminous Shrub ( Caragana microphylla) in Semiarid Sandy Soils of North China

Caragana microphylla Lam., a pioneer leguminous shrub species for vegetation re-establishment, is widely distributed in the semi-fixed and fixed sandy lands of the Horqin region. Some soil chemical and physical properties were measured under the canopy of C. microphylla and in the adjacent open areas to determine the effects of individual shrubs on soil properties. The influence of isolated C. microphylla on chemical and physical properties of the topsoil was significantly different between plots under the shrub canopy and in the shrub interspaces. Beneath the shrub canopy greater amounts of fine particle fractions, a higher water-holding capacity, and a lower bulk density, as well as higher aboveground and belowground litter biomass were found. Soil organic C and total N concentrations were 23%-31.6% and 14%-27.2% higher under the shrub canopies than in the shrub interspaces, respectively, giving rise to ”islands of fertility”. In a desertified sandy grassland ecosystem, C. microphylla was believed to play a major role in organic C sequestration, N accumulation, and the hydrologic cycle. Additionally, it has been found to be of ecological importance for vegetative restoration and reversal of desertification.

Formation, distribution and ecological consequences of flood-related wood debris piles in a bedrock confined river in semi-arid South Africa

The Sabie River, located within the semi-arid savanna of South Africa, experienced a ∼100-year return interval flood in 2000, providing a rare opportunity to quantify the resultant pattern and consequence of woody debris piles for riparian areas. Biophysical attributes of rivers in arid and semi-arid regions differ strongly from those in mesic regions, but differences in the role and dynamics of woody debris remain largely unknown. Our primary goal was to determine the basic ecology and distribution of wood piles formed by a large infrequent flood in a bedrock-confined river. In particular, we sought to determine the mechanism of pile formation, their position, size, and structural attributes of piles as well as regeneration from resprouting and seedling recruitment within piles in different channel types. We observed relatively distinct patterns of distribution and mechanisms of formation in 421 piles and provide a description of the distribution, abundance and short-term fate of each pile type. Patterns of wood accumulation were largely controlled by characteristics of the trapping sites, particularly toppled trees that remain rooted in their growth location. In general, wood was primarily strewn against toppled, transported and standing trees, though several large piles formed on bedrock outcrops. Buried piles were also discovered upon excavation of depositional features (alluvial mounds). Resprouting of toppled trees with intact roots and living tissues was the dominant mode of vegetation reestablishment in the piles. We observed resprouting in 36% of piles surveyed. Resprouting piles were most common (48%) in the seasonally inundated portion of the macro-channel. Tree seedlings were recorded in 28% of the piles. The flood appeared to create heterogeneity in the establishment of new woody vegetation by forming distinct wood piles from the ruins of the previous riparian forest. Even though the input of wood to semi-arid rivers appears to be a fairly rare occurrence and wood piles are rapidly depleted by decay and fire, we expect their influence will be long-lived, preserved in the pattern of vegetation establishment and alluvial mounds within the macro-channel. Copyright © 2006 John Wiley & Sons, Ltd.

How a wet tropical rainforest copes with repeated volcanic destruction

The Holocene Period for the province of West New Britain, Papua New Guinea, is characterised by periodic catastrophic volcanism. The region is mantled in dense wet tropical rainforest, and has been occupied by people since the Pleistocene. Analyses of peat from two nearby sites within a lowland rainforest environment provide us with a macro-level landscape account of the periodic destruction and recovery of the coastal forests during seven periods of volcanic activity in the latter part (∼2900 yr ago to present) of the Holocene. Radiocarbon dating shows the very close correlation of the peat and tephra layers at both sites, yet the pollen analysis reveals different vegetation communities. These initial results allow us to begin identifying the processes of recovery, and to recognise different ecological pressures placed on vegetation at these neighbouring sites. Evidence of hydrological changes are observed beginning with a marine incursion recorded at Garu Site 3 ∼1360 14C yr B.P. The distinct differences in the vegetation re-establishment and community regeneration rates suggest the greater level of disturbance at Garu Site 1 could be related to the depth of the ashfall, although the proximity of a known human settlement may also be a contributing factor. Of note, palynologically, we found that the fern spore flora is particularly rich and believe it will be useful for ecological interpretation.

Restoration of Arthropod Assemblages in a Spartina Salt Marsh following Removal of the Invasive Plant Phragmites australis

Abstract Invasive plants are one of the most serious threats to native species assemblages and have been responsible for the degradation of natural habitats worldwide. As a result, removal of invasive species and reestablishment of natural vegetation have been attempted in order to restore biodiversity and ecosystem function. This study examined how native arthropod assemblages, an abundant and functionally important group of organisms in many ecosystems, are affected by the incursion of the invasive wetland plant Phragmites australis and if the restoration of the native vegetation in brackish Spartina alterniflora marshes results in the reestablishment of the arthropod community. The invasion of Phragmites into a coastal Spartina marsh in southern New Jersey seriously altered arthropod assemblages and trophic structure by changing the abundance of trophic groups (detritivores, herbivores, carnivores) and their taxonomic composition. Herbivore assemblages shifted from the dominance of external free‐living specialists (e.g., planthoppers) in Spartina to concealed feeders in Phragmites (stem‐feeding cecidomyiids). Moreover, free‐living arthropods in Phragmites became dominated by detritivores such as Collembola and chironomids. The dominant marsh spiders, web‐building linyphiids, were significantly reduced in Phragmites habitats, likely caused by differences in the physical environment of the invaded habitats (e.g., lower stem densities). Thus, trophic structure of arthropod assemblages in Phragmites, as seen in the large shifts in feeding guilds, was significantly different from that in Spartina. Removal of Phragmites with the herbicide glyphosate resulted in the rapid return of Spartina (≤5 yrs). Moreover, return of the dominant vegetation was accompanied by the recovery of most original habitat characteristics (e.g., live and dead plant biomass, water flow rate). The arthropod assemblage associated with Spartina also quickly returned to its preinvasion state and was not distinguishable from that in uninvaded Spartina reference sites. This study provides evidence that the reestablishment of native vegetation in areas previously altered by an invasive plant can result in the rapid recovery of the native arthropod assemblage associated with the restored habitat.

Anthropogenic disturbances and plant biodiversity in forests of Uttaranchal, central Himalaya

Eight forest types varying in disturbance frequencies were identified along an elevational gradient in Uttaranchal, central Himalaya. Low elevation forests were close to human habitation and had high disturbance frequency, while high elevation forests were situated far from the human habitation and had low disturbance. The dominant tree species at low elevation were Pinus roxburghii and Quercus leucotrichophora, while Q. floribunda and Q. semecarpifolia dominated the high elevation forests. Pyracantha crenulata was the shrub present in all the forests except in Q. semecarpifolia forest and Anaphalis contorta, a herb species, was present in all the forests. Disturbance decreased the dominance of single species and increased the plant biodiversity by mixing species of different successional status. Species richness and diversity for all the vegetation layers were higher in low elevation–high disturbance forests. Mean tree density decreased from high to moderate and increased in low disturbance. The shrub density decreased from high to low disturbance while the reverse occured for herbs. High proportion of early successional species in disturbed forests indicated that disturbance induces succession. The mean number of young individuals increasing from high to low disturbance indicates that disturbance adversely affects regeneration. But, however, the high number of young individuals of Coriaria nepalensis, a small non-leguminous nitrogen fixing tree, in disturbed forests shows that the forest is regenerating. This species could be helpful in the re-establishment of original vegetation through triggering the regeneration of these forests. High elevation–low disturbed forests separated from low elevation–high disturbed forests. Forest type and elevation may have more influence on tree richness while shrub and herb richness may be more sensitive to disturbance and forest types.

Social persistence of plant-based management of dryland salinity

Rural areas of Australia are undergoing rapid social and economic transformations, creating a divergence between those rural landscapes that are depopulating and those that are repopulating. In the depopulating landscape of the cropping zones at risk to salinity, the new paradigm of salinity management based on the development of new plant production systems may be the best strategy available. We suspect this strategy will be less suited to the repopulating rural areas, where amenity is a major factor in population growth. In these landscapes, investment in recharge control based upon commercial pasture production or plantation forest industries is unlikely to be socially compatible with the aspirations of future residents. Strategies aimed at low-cost re-establishment of native vegetation may be more appropriate, but will still be limited in their application. Any discussion of the sustainability of plant-based management systems for dryland salinity needs to include not only biological or agronomic persistence, but also social persistence.