Revegetation Of Areas Research Articles

절개사면 녹화지역과 인접 자연지역의 식생 비교

This study was compared to the differences in the habitat, species composition and community structure of revegetation and nature area in Korea. Plant number in plot of revegetation and nature area was 10.3 and 15.0 taxa, respectively, and coverage was 90.6 and 88.1%, respectively. Revegetation and nature area was very heterogeneous, due to low similarity index (0.38) and less common plants. Festuca arundinacea frequency (56.7%) was highest in revegetation area, and Oplismenus undulatifolius frequency (66.7%) was highest in nature area. Plant appearing of revegetation and nature area was 111 and 136 taxa, respectively. Herb appearing of revegetation and nature areas was 93 (83.3%) and 72 (52.9%) taxa, respectively, tree was 18 (16.2%) and 64 (47.1%) taxa, respectively. Plant communities of revegetation area was classified into Lespedeza bicolor, Indigofera amblyantha, Alnus sibirica, Festuca arundinacea, Eragrostis curvula, Miscanthus sinensis, Humulus japonicus, Setaria faberii, Rudbeckia bicolor, Pueraria lobata community. Plant communities of nature area was classified into Pinus densiflora, Quercus aliena, Quercus acutissima, Quercus variabilis, Quercus serrata, Castanea crenata, Pinus rigida, Robinia pseudoacacia, Populus tomentiglandulosa, Phyllostachys bambusoides community. Habitat, species composition and community structure of revegetation and nature area showed a large difference.

Responses of soil moisture in different land cover types to rainfall events in a re-vegetation catchment area of the Loess Plateau, China

Implementation of the Grain-for-Green project has resulted in significantly increased vegetative cover on the Loess Plateau of China during the past few decades. The plant communities influence soil moisture recharge and usage processes, particularly the input process, which is directly related to transformation of the limited precipitation into available soil water in the semi-arid Loess Plateau. A study to measure soil moisture dynamics of typical land cover types associated with precipitation events was conducted in a re-vegetated catchment area. Smart probes were inserted at 6 different depths below the ground surface under grass ( Andropogon ), subshrub ( Artemisia scoparia ), shrub ( Spiraea pubescens ), tree ( Robinia pseudoacacia ), and crop ( Zea mays ) vegetation to record volumetric soil moisture at 10-minute intervals for a period of 60 days during the growing season in 2011. The advance of the wetting front and total accumulated infiltrated water were measured. The rainfall events were sporadic with widely different intensities, and the soil moisture was replenished mainly by 3–4 heavy precipitation events during July and August. The mean soil moisture content profiles of the 5 vegetation types can be ordered as crop > grass > subshrub > tree > shrub and this relationship displayed time stability. The different land cover types clearly influenced the water infiltration and water input amounts in the re-vegetated area. The subshrub site showed the highest total infiltration amount (164 mm) with precipitation (227 mm) during the study period. The grass site had an infiltration amount of 156 mm. The tree site had a total precipitation of 154 mm and an infiltration amount of 97 mm. The infiltration amount was 136 mm for the shrub site and was the lowest (83 mm) for the crop site. Natural grasses displayed a rapid infiltration rate and the wetting front was able to reach a greater depth. ► We observe the water infiltration processes under a heavy rainfall. ► We compare the effects of different soil moisture inputs of five plant species. ► The mean soil moisture relationship displayed time stability. ► Natural grasses displayed a rapid infiltration rate and reach a greater depth.

Temporal and spatial variations in soil organic carbon sequestration following revegetation in the hilly Loess Plateau, China

Abstract Land use change is one of the major factors that affect soil organic carbon (SOC) variation and global carbon balance. Since the late 1970s, a significant area of the hilly Loess Plateau has undergone major land use changes during several revegetation programs, especially in the Grain for Green Project. However, so far there has not been a comprehensive study to determine temporal and spatial variations in SOC due to revegetation in this region, which hampers accurate predictions of the SOC sequestration potential and the land use change impacts. In this study, slope cropland and five typical revegetation types in the hilly Loess Plateau were selected, and then classified into 36 groups according to different revegetation years and landforms to investigate temporal and spatial variations of SOC and the impacts of relevant factors following revegetation. The results showed that the SOC concentration in the top soil horizon (0–5 cm) increased most significantly with revegetation and that increases in SOC slowed with increasing soil depth, but coefficient of variations in different soil horizons indicated that revegetation could cause SOC concentration differences at up to a 30 cm depth. Temporal variation in SOC occurred in two main phases in replanted cropland: in the first 10 or 15 yr, the profile mass of SOC (SOC density, SOCD) increased slightly; after this phase, SOCD increased significantly, with sequestration rates of 0.69, 0.55 and 0.24 t·ha − 1 ·yr − 1 (revegetation 10 to 35 yr) for planted woodland, planted shrubland and abandoned cropland, respectively. The SOC sequestration rate in wild grassland was 0.23 t·ha − 1 ·yr − 1 (revegetation 10 to 35 yr), which was similar to that in abandoned cropland. In contrast, the SOCD in wild shrubland increased rapidly in the first 10 yr, with a rate of 0.93 t·ha − 1 ·yr − 1 , and then by 0.56 t·ha − 1 ·yr − 1 over the next 25 years. SOCD spatial differences in different landforms had reached several times the annual SOCD increment and followed a new trend after revegetation: SOC sequestration in shady slope areas was significantly higher than in sunny slope areas, but no significant difference was found between gentle slopes and steep slopes after revegetation. A general linear model was used to identify the factors that were most relevant to SOC variation. Revegetation years accounted for nearly half of the total contribution to SOC variation (42%), and land use type was responsible for 33% of SOC variation. SOCD distribution in a watershed confirmed that variables of land use and years after revegetation dominated SOC variation. Landforms had a small influence on SOC variation at the regional scale, but the influence of the slope aspect was still large. The SOC sequestration rate was about 0.21 to 0.64 t·ha − 1 ·yr − 1 with revegetation in the hilly Loess Plateau, which was highest in wild shrubland, followed by planted woodland, planted shrubland, abandoned cropland and wild grassland. Considering the large area of revegetation and relatively high SOC sequestration rate, SOC sequestration in this region should contribute significantly to decreasing the carbon concentration in atmosphere.

Assessing heavy metal pollution in the water level fluctuation zone of China’s Three Gorges Reservoir using geochemical and soil microbial approaches

The water level fluctuation zone (WLFZ) in the Three Gorges Reservoir is located in the intersection of terrestrial and aquatic ecosystems, and assessing heavy metal pollution in the drown zone is critical for ecological remediation and water conservation. In this study, soils were collected in June and September 2009 in natural recovery area and revegetation area of the WLFZ, and geochemical approaches including geoaccumulation index (I (geo)) and factor analysis and soil microbial community structure were applied to assess the spatial variability and evaluate the influence of revegetation on metals in the WLFZ. Geochemical approaches demonstrated the moderate pollutant of Cd, the slight pollutant of Hg, and four types of pollutant sources including industrial and domestic wastewater, natural rock weathering, traffic exhaust, and crustal materials in the WLFZ. Our results also demonstrated significantly lower concentrations for elements of As, Cd, Pb, Zn, and Mn in the revegetation area. Moreover, soil microbial community structure failed to monitor the heavy metal pollution in such a relatively clean area. Our results suggest that revegetation plays an important role in controlling heavy metal pollution in the WLFZ of the Three Gorges Reservoir, China.

Seasonal variation of carbon exchange from a revegetation area in a Chinese desert

Revegetation is a common method to combat desertification and to reduce soil carbon loss in arid and semi-arid areas worldwide. Revegetated areas in the temperate arid Shapotou area of Northern China were established to stabilize sand dunes in an area subject to wind erosion. The objective of this study was to characterize the carbon flux of a 20-year old revegetated area. During the measurement period from May 2008 to December 2010 carbon flux was measured by the eddy covariance technique, and rainfall, temperature, and soil water content were monitored simultaneously with the aim of understanding the relationship between carbon flux and meteorological factors. We found that the revegetated ecosystem is a carbon sink during the growing season when most of the annual precipitation falls. The revegetated area changed from being a carbon source to a sink in the 1 or 2 days following an effective rainfall event. In the non-growing season the ecosystem was a carbon source. The soil water content (SWC) affected the relationship between ecosystem respiration and temperature. The nighttime respiration rate increased with soil temperature. When the SWC was ≥3% the correlation between respiration rate and soil temperature was stronger (R2=0.23) than when SWC was <3% (R2=0.08). Although the net ecosystem carbon flux (NEE) in temperate arid desert areas is relatively small compared to that of humid areas, it represents huge carbon fixation potential because of the very large area of desert in northern China. Further research is required to clarify the effects of climatic factors on the various components of temperate arid ecosystems, especially the roles of cryptogam and biological soil crusts in the carbon exchange processes.

Soil Moisture Research of Revegetation Area on Slop of Yingrui Highway in the Spring

The research object is slop near Yingrui highway, we mainly used oven drying method, combined with TDR, carrying out different vegetation types in interchange area and different substrates types in slope area about dynamic monitoring soil moisture in the spring. According to the result, The daily dynamic of the 2 types of slop soil moisture content has no obvious regular pattern, but each time the moisture content in soil slope are higher than rocky slope. We can get the conclusion after variance analysis, the main factors which influencing the discretion of the soil moisture content in slope and interchange area are the slope matrix type and the different vegetation reconstruction mode in interchange area. Meanwhile, according to the data, which we applied to the same experiment with both TDR and oven drying method, and after comparative analysis, we think, it’s completely effective to make TDR applied in deep soil moisture determination in some places such as interchange area, but the data about shallow soil moisture determination which got from the places such as in side slope is inaccurate. We should be more cautious when using it.

Phytostabilization of semiarid soils residually contaminated with trace elements using by-products: Sustainability and risks

We investigated the efficiency of various by-products (sugarbeet lime, biosolid compost and leonardite), based on single or repeated applications to field plots, on the establishment of a vegetation cover compatible with a stabilization strategy on a multi-element (As, Cd, Cu, Pb and Zn) contaminated soil 4–6 years after initial amendment applications. Results indicate that the need for re-treatment is amendment- and element-dependent; in some cases, a single application may reduce trace element concentrations in above-ground biomass and enhance the establishment of a healthy vegetation cover. Amendment performance as evaluated by % cover, biomass and number of colonizing taxa differs; however, changes in plant community composition are not necessarily amendment-specific. Although the translocation of trace elements to the plant biotic compartment is greater in re-vegetated areas, overall loss of trace elements due to soil erosion and plant uptake is usually smaller compared to that in bare soil.

The influence of patch area and connectivity on avian communities in urban revegetation

Landscape restoration through revegetation is being increasingly used in the conservation management of degraded landscapes. To effectively plan restoration programs information is required on how the landscape context of revegetation influences biodiversity gains. Here, we investigate the relative influence of patch area and connectivity on bird species richness and abundance within urban revegetation patches in Brisbane, Australia. We carried out bird surveys at 20 revegetation sites, and used hierarchical partitioning and model selection to test the relative importance of patch area (the area of revegetation including all directly connected remnant vegetation) and landscape connectivity (the vegetated area connected by less than 10m, 20m, 30m, 40m and 50m cleared gaps). We controlled for a number of possible confounding variables within the hierarchical partitioning procedure. Both the hierarchical partitioning and model selection procedures indicated that connectivity had an important influence on bird species richness. Patch area in combination with connectivity were important influencing factors on overall bird abundance. We also carried out the hierarchical partitioning procedure for bird abundance data within a range of feeding guilds, yielding results specific to species groups. Overall our data suggest that greater connectivity enhances the habitat area that colonists can arrive from (resulting in greater species richness), whereas increased patch area allows for increased abundance by expanding the habitat available to species already present in a patch. A combined approach where connectivity and overall habitat area is enhanced across the landscape is likely to be necessary to meet long-term conservation objectives.

KARAKTERISTIK PEDOLOGI DAN PENGELOLAAN REVEGETASI LAHAN BEKAS TAMBANG NIKEL: STUDI KASUS LAHAN BEKAS TAMBANG NIKEL POMALAA, SULAWESI TENGGARA

&lt;p&gt;Post-mining land management needs to be done by taking into account a holistic approach concerning the improvement of physical, chemical and biological properties of soil as growth media, in order to support the rehabilitation plans. The objective of this study were: (i) to conduct quantitative and comprehensive an inventory of pedological properties of nickel post mining land, (ii) to analyze the potential and limitations of post mined land, (iii) act designed environmental management, based on the characteristics of the revegetation of the land and the environment. The results showed that the soil in Pomalaa could be classified in Typic Hapludox, clayey, mixed, isohypertermic (P1) dan Typic Hapludalfs, loamy, mixed, isohypertermic (P2), while the material in ex mining area are overburden or parent material. The soil has developed from peridotite and peridotite-serpentinite ultramafic material. This soil has low natural fertility and require efforts to improve the physical properties. Ex-mining area has a high rate of erosion. Poor tree growth in revegetation area has been determined caused by a deficiency of Ca, Fe, Cu, or Mn. The possibility of Ni and Cr toxicity in plants needs to be further investigated. Local resources in the form of slag can be used for revegetation, especially converter slag. The results obtained from this study can be used to give the advice of post-nickel mining land management, based on land characteristics. A better management advice covers two issues, namely improvements of the management action actually implemented and improvements in technical rehabilitation.&lt;br /&gt;Keywords: Pedological processes, post nickel mining land, revegetation&lt;/p&gt;

Mapping Postfire Vegetation Recovery Using EO-1 Hyperion Imagery

The aim of this paper is to investigate whether it is possible to accurately map postfire vegetation recovery on the Mediterranean island of Thasos by employing Earth Observing-1 (EO-1) Hyperion imagery and object-based classification. Specific objectives include the following: 1) locating and mapping areas of forest regeneration and other vegetation recovery and distinguishing among them; 2) distinguishing between <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Pinus brutia</i> regeneration and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Pinus nigra</i> regeneration within the area of forest regeneration; and 3) examining whether it is possible to distinguish between areas of forest regeneration ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Pinus brutia, Pinus nigra</i> ) and mature forest. The data used in this study consist of satellite images, field-spectroradiometry measurements, and field observations of the homogenous revegetated areas. The methodology comprised four consecutive steps. The first step involved preprocessing of the Hyperion image and field data. Subsequently, an object-oriented model was developed, which involved three steps, namely, image segmentation, object training, and object classification. The process resulted in the separation of five classes (¿ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">brutia</i> mature,¿ ¿ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nigra</i> mature,¿ ¿ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">brutia</i> regeneration,¿ ¿ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nigra</i> regeneration,¿ and ¿other vegetation¿). The accuracy assessment revealed very promising results (approximately 75.81% overall accuracy, with a Kappa Index of Agreement of 0.689). Some classification confusion involving the classes of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Pinus brutia</i> regeneration and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Pinus nigra</i> regeneration was recorded. This could be attributed to the absence of large homogenous areas of regenerated pine trees. The main conclusion drawn in this paper was that object-based classification can be used to accurately map postfire vegetation recovery using EO-1 Hyperion imagery.

O papel da comunidade de fungos micorrízicos arbusculares (FMA) autóctones no desenvolvimento de espécies vegetais nativas em área de dunas de restinga revegetadas no litoral do Estado da Paraíba

A simbiose entre fungos micorrizicos arbusculares (FMA) com raizes de plantas vasculares constitui uma das mais importantes formas de mitigar o impacto das areas pertubadas. O trabalho objetivou caracterizar a comunidade de FMA presente no solo de area de duna revegetada e avaliar sua influencia sobre o desenvolvimento de especies nativas. Foi realizada coleta de solo durante o periodo chuvoso em area revegetada, avaliando-se: producao de proteinas do solo relacionadas a glomalina (PSRG), densidade e diversidade de glomerosporos. A influencia da comunidade nativa de FMA foi determinada para duas especies vegetais nativas: Tabebuia roseo-alba (Ridl.) Sandw. (peroba) e Tocoyena selloana Schum. (jenipapo-bravo). Para cada especie foram testados dois tratamentos - solo nativo (SN) e solo nativo desinfestado (SND) - em delineamento inteiramente casualizado com 10 repeticoes. Ao final foram avaliados: altura, diâmetro do caule, numero de folhas, area foliar, biomassa seca e conteudo de nutrientes nas partes aerea e radicular, densidade de glomerosporos, colonizacao micorrizica hifalica, arbuscular, vesicular e total e producao de proteinas do solo relacionadas a glomalina (PSRG). O solo da area de duna revegetada apresentou 1 glomerosporo g-1 de solo e 1,20 ± 0,04 mg PSRG g-1 solo, sendo identificadas seis especies de FMA. Maior desenvolvimento vegetal e fungico ocorreram no SN. A colonizacao micorrizica na peroba foi de 80% e no jenipapo-bravo 60%. Os FMA estao presentes em areas revegetadas apos extracao de minerios, e contribuem para o crescimento das especies nativas testadas em condicoes de casa de vegetacao, sugerindo assim, que o desempenho dessas plantas e influenciado pela simbiose micorrizica arbuscular.

Linking ecological function to species composition in ecological restoration: Seed removal by ants in recreated woodland

AbstractEvaluations of ecological restoration typically focus on associating measures of structural properties of ecosystems (e.g. species diversity) with time since restoration efforts commenced. Such studies often conclude a failure to achieve restoration goals without examining functional performance of the organism assemblages in question. We compared diversity and composition of ant assemblages and the rates of seed removal by ants in pastures, 4‐ to 10‐year old revegetated areas and remnants of Cumberland Plain Woodland, and an endangered ecological community in Sydney, Australia. Ant assemblages of forest remnant sites had significantly higher species richness, significantly different species composition and a more complex functional group structure in comparison with ant assemblages of pasture and revegetated sites, which did not differ significantly. However, the rates of seed removal by ants in revegetated sites were similar to those in forest remnants, with the rates in pasture sites being significantly lower. Approximately, one‐third of all ant species were observed to remove seeds. Forest remnant sites had significantly different assemblages of seed removing ant species from those in pasture and revegetated sites. These results demonstrate that similar ant assemblages of unrestored and restored areas can function differently, depending on habitat context. Evaluation of restoration success by quantifying ecosystem structure and function offers more insights into ecosystem recovery than reliance on structural data alone.

Are native birds using revegetated areas? Insights from the Western Australia central wheatbelt

Are native birds using revegetated areas? Insights from the Western Australia central wheatbelt

Responses of biological soil crusts to sand burial in a revegetated area of the Tengger Desert, Northern China

Little information is available regarding the responses of biological soil crusts to sand burial in desert ecosystems. Therefore, in this study, we evaluated the effects of sand burial (sand depth of 0, 1, 2, 3 and 4 mm) followed by simulated precipitation (1, 3 and 5 mm distilled water, sprayed at 2-day intervals) on CO 2 exchange and growth by four types of crust collected from a revegetated area of the Tengger Desert (Northern China) in 2007. The results revealed that the respiration rate was significantly decreased and that moss shoot elongation was significantly increased ( P < 0.001) following burial. Both of these responses may have acted as compensatory mechanisms that favoured the recovery of crust after burial. The burial responses among the four crusts were also compared by measuring the cryptogam cover variations after burial and then computing the speed of emergence and a tolerance index (by standardizing the speed of emergence with a burial ratio of sand burial depth to the initial maximum height of the crust). Among the four crusts evaluated, Bryum argenteum crust showed the fastest speed of emergence (average 11.5% cover week −1) and highest tolerance index (average 0.182), followed by Didymodon vinealis crust (emergence, 11.3% week −1; tolerance, 0.129), Syntrichia caninervis crust (emergence, 7.7% week −1; tolerance, 0.097) and Collema tenax crust (emergence, 4.2% week −1; tolerance, 0.022). This sequence was in agreement with the successional order of these crusts that has been observed in the revegetated area evaluated in this study, which suggests that sand burial is one of the most important factors driving the succession of crusts in desert ecosystems. Furthermore, water played a role in the recovery process, as evidenced by pronounced decreases in dark respiration and increases in photosynthesis, speed of emergence and tolerance index for each crust type, as well as by shoot elongations by three mosses in response to the accretion of water. The restriction of tolerance against sand burial under limited precipitation conditions emphasizes the necessity for sand-binding measures to alleviate the negative effects of sand burial on crusts, which are crucial to preventing revegetated areas from undergoing desertification.

Who's planting what, where and why – and who's paying?: An analysis of farmland revegetation in the central wheatbelt of Western Australia

Landholders in the neighbouring Wallatin and O’Brien Creek catchments of the central wheat belt of Western Australia have planted 1750 ha of woody perennial vegetation in the catchments from the 1920s to 2006, adding 4.6% further cover to the 9.4% cover of uncleared remnant native vegetation. Landholders attribute most plantings to two or more motives with salinity mitigation and nature conservation the largest drivers of revegetation (27% and 22% by area, respectively), but soil erosion and aesthetics are also important. The location and spatial arrangement of revegetation in the landscape reflects these motives. Most of the vegetation comprises mixed native tree species (44%) or saltbush (31%) and different types of revegetation are associated with different motives and have different histories of planting popularity. Most revegetation (77%) has been funded privately by landholders, either entirely (49% of the total area) or in plantings subsidised by government funds (41% of the total area). Individual farmers differ markedly as to both the area of revegetation on their properties and the ratio of private to public funding. The data indicate that landholders in these catchments believe they have undertaken as much revegetation as can be economically justified and that they effectively ceased planting activities in 2004. Further revegetation activities in these catchments are likely to be contingent upon the development of profitable agroforestry options.

Tolerance of two perennial grasses to toxic levels of Ni2+

Environmental context. Nickel (Ni) may be present in soil at phytotoxic levels as a result of weathering of ultramafic (serpentine) minerals or activities such as mining and metal ore processing. We assessed the tolerance of two grasses to excess Ni and used electron microscopy to examine the distribution of the Ni within the root tissue. This study provides information on the influence of excess Ni on the growth of these two grasses with consideration to their suitability for the revegetation of areas contaminated with Ni. Abstract. Toxic effects of Nickel (Ni) in solution were evaluated in signal grass and Rhodes grass, two species commonly used for the revegetation of contaminated sites in the tropics and sub-tropics. Both grasses had a similar response to Ni, a Ni2+ activity ({Ni2+}) of 14 × 10–6 M, which reduced the fresh mass by 50%. The sub-cellular distribution of Ni in the roots was similar for both species, with Ni accumulating primarily as particles &lt;5 nm in the vacuoles of rhizodermal and outer cortical cells. The reduction in growth at elevated {Ni2+} caused a loss of apical dominance in the roots and a Ni-induced Fe deficiency in the shoots. Root hair growth was not reduced by Ni2+ toxicity and was prolific even at the highest {Ni2+} (35 × 10–6 M). The translocation of Ni to the plant tops of both grasses resulted in concentrations that exceeded the guidelines for Ni toxicity to grazing animals (100 μg g–1) when grown with ≥11 × 10–6 M {Ni2+} in solution.

Application of a Molecular Method for the Identification of a Gigaspora margarita Isolate Released in a Field

A molecular technique for the identification of the Gigaspora margarita isolate CK based on the detection of a DNA sequence of 235 bp as its diagnostic marker was evaluated to investigate the survival and establishment of introduced arbuscular mycorrizal fungi (AMF) in a field ecosystem. In March 2001, roots and rhizosphere soil of Eragrostis curvula and Miscanthus sinensis were collected from the Mizunashi River at Mt. Fugendake (Nagasaki Prefecture, Japan), where plant seeds and AMF including G. margarita CK had been introduced for reforestation after the occurrence of repeated pyroclastic flows. We detected the marker sequence from DNA preparations of E. curvula roots and Gigaspora spores in the rhizosphere. This clearly showed that the isolate occurred at both hyphal and sporal stages. It was shown that the isolate survived and developed a life cycle in the revegetation area for 4 years. It was confirmed that the method was effective for tracing the isolate in samples collected from field ecosystems.

Water balance change for a re-vegetated xerophyte shrub area/Changement du bilan hydrique d’une zone replantée d’arbustes xérophiles

Water balances for a re-vegetated xerophyte shrub (Caragana korshinskii) area were compared to that of a bare surface area by using auto-weighing type lysimeters during the 1990–1995 growing seasons at the southeast Tengger Desert, Shapotou, China. The six-year experiment displayed how major daily water balance components might vary for a bare and a re-vegetated sand dune area. Evapotranspiration from the C. korshinskii lysimeter represented a major part of the water balance. The average annual ET/P ratios varied between 69 and 142%. No seepage was observed for the vegetated lysimeter. For the bare lysimeter, on the other hand, 48 mm or 27% of observed rainfall per year occurred as seepage. These results suggest that re-vegetating large sandy areas with xerophytic shrubs could reduce soil water storage by transpiration. Also, the experimental results indicate that re-vegetating large sandy areas could significantly change groundwater recharge conditions. However, from a viewpoint of desert ecosystem reconstruction, it appears that natural rainfall can sustain xerophytic shrubs such as C. korshinskii which would reduce erosion loss of sand. However, re-vegetation has to be balanced with recharge/groundwater needs of local populations.

Soil seedbanks in natural and restored boxironbark forests at Stawell Gold Mine, Victoria

Natural communities have the capacity to regenerate themselves, and this functional ecosystem attribute must be regarded as a key indicator of success for revegetation programmes. The accumulation of species (and individuals) as dormant propagules in a soil seedbank, representing potential future states for the vegetation, is one possible index of revegetation success. Here, we investigate the soil seedbanks for five natural vegetation (Box-Ironbark forest) remnants, a topsoil stockpile and three revegetated mine-site areas associated with gold mining at Stawell (Victoria, Australia). The revegetation efforts largely date from 1987 and, in terms of their composition and structure, are relatively similar to natural vegetation remnants. Soil samples were treated with heat or smoke (plus control) and were monitored for seedling emergence, species composition and density in the glasshouse for 150 days. Seedling densities in treated seedbank samples were high (2 200 to 17 500 seedlings m-2) while species richness was low, ranging from 10 to 20 species per sample. Exotic species made up 22?61 % of emergents and 33?50% of species observed. Correlation of seedbank composition and density with chemical attributes of soils, and with above ground (extant) vegetation at sites showed few significant relationships. Total species richness and the proportion of exotic species varied significantly between natural bushland remnants and revegetation areas. Richness was highest, and the proportion of exotic species was lowest in natural bushland samples. Total emergent numbers and the density of exotic emergents did not vary significantly between remnant bushland and revegetation areas. Declining vigour of some woody species in revegetation sites that are well represented in the seedbank, including Acacia pycnantha and A. genistifolia, indicates that the reintroduction of fire might be an appropriate management practice to facilitate long-term recovery of a functional community on these revegetated surfaces, but the potential for the establishment of weed species from the seed-bank following fire may pose a challenge to management.

The biology of Canadian weeds. 121. Galium mollugo L.

Galium mollugo L. (smooth bedstraw) is a long-lived perennial broadleaved plant that reproduces both vegetatively and by seed. Galium mollugo can be a strong competitor in long-lived forage crops such as bird’s-foot trefoil (Lotus corniculatus L.), timothy (Phleum pratense L.), and orchard grass (Dactylis glomerata L.), as well as in short-lived forage crops such as red clover (Trifolium pratense L.) and yellow sweet-clover [Melilotus officinalis (L.) Lam.]. It is also a problem weed in spruce plantations and re-vegetation areas. Livestock typically avoid this species, allowing it to become well-established in pastures where it outcompetes more favourable species. Moreover, G. mollugo is viewed as a successful invasive species because of its ability to colonize and proliferate in areas such as established meadows where most invasive species do not thrive. In natural meadow communities, G. mollugo is often a dominant species that is capable of colonizing areas left vacant by the death and/or displacement of other species. Under favourable conditions, G. mollugo growth and clonal expansion can increase rapidly. Galium mollugo is generally tolerant to herbicides such as 2,4-D, MCPA, 2,4-DB, and dicamba. Key words: Smooth bedstraw, GALMO, Galium mollugo, Rubiaceae, weed biology, pastures