bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in dry matter and nutrient yields during the restoration of species‐rich grasslands
Authors: Oomes M. J. M. 
Published: May 2006

Abstract. In two moderately productive grasslands that had been withdrawn from agricultural use, one on humic sandy soil and one on heavy clay, the decrease in dry matter, N‐, P‐ and K‐yields were measured for 14 and 11 years respectively, after fertilization had been stopped. The grasslands were mown twice a year. The yields and concentrations of nutrients were compared with those of already unproductive grasslands under the same growing conditions.On sandy soil, the annual dry matter yield decreased from 10.2 to 6.5 ton / ha in four years. After nine years, the dry matter (4.1 ton / ha) and K (20.5 kg / ha) yields were as low as those of the unproductive grassland. At that time yields and concentrations of N and P were still greater. The low K‐ concentration of 0.50 % and the lack of response upon N fertilizing indicate that the supply of K limits biomass production.On clay, during the first three years, the dry matter yield decreased from 10.2 to 5.0 ton / ha, after 6 yr the production increased again. The low N‐concentration of 1.52 % after 10 yr indicates that N is likely to limit biomass production, but the low P‐concentration of 0.14% indicates that P shortage can also be expected. In the lower productive grassland on sand the number of species that invaded was higher.
Seed bank dynamics of Mediterranean pastures subjected to mechanical disturbance
Authors: Levassor C. , Ortega M. , Peco B. 
Published: May 2006

Abstract. Vegetation and buried germinable seeds were examined in Mediterranean pastures differing both in time elapsed since last ploughing and in intensity of disturbance. Densities of buried germinable seeds in the greenhouse were determined from 10 × 10 × 3 cm soil cores taken during the autumn prior to the time of germination. Abundance of pasture species was recorded on the same sites during the following spring.The species composition of the seed bank was very similar to that of the vegetation: 80.9 % similarity (Sorensen's index). The number of species and density of buried seeds ready to germinate increased with suc‐cessional age from 0 to 4 yr and decreased later to a constant level after 9 yr. Regarding disturbance intensity, the highest species numbers are found at intermediate intensities while there is a drastic decrease at high disturbance intensity. The floristic composition of the seedbankwas analyzed through Correspondence Analysis (CA) and Binary Discriminant Analysis (BDA). Seed bank composition reflected both successional stage and intensity of disturbance. Characteristic species of both gradients were identified.
Changes in soil characteristics in eucalypt plantations replacing natural broad‐leaved forests
Authors: Bargali S. S. , Singh R. P. , Joshi Mukesh 
Published: May 2006

AbstractProperties of the top 30 cm of soil under plantations of 1‐yr to 8‐yr old Eucalyptus (the hybrid E. tereticornis) and in adjacent natural mixed broad‐leaved forest were compared in the sub‐tropical zone of the central Himalaya. Various soil‐physical characteristics decreased with increasing age; soil‐chemical properties, notably organic carbon, total N, P and K decreased as a result of reforestation with Eucalyptus and further decreased with increasing age of the plantation.
Vegetation‐environment relationships in a Negev Desert erosion cirque
Authors: Ward David , Olsvig‐Whittaker Linda , Lawes Michael 
Published: May 2006

AbstractThe relationship of desert vegetation to topographic and edaphic factors in Makhtesh Ramon, an erosional cirque in the Negev Desert of Israel, was analyzed using redundancy analysis ordination. Altitude and geological substrate had the most significant correlations with vegetation patterns. In particular, significant and monotonic increases in both total species richness and the percentage of annual species were found with increasing altitude. A comparison was made of the effectiveness of Whittaker's diversity sampling plots (Shmida 1984) versus the log‐series survey method of McAuliffe (1990). We concluded that at small sample sizes, the Mc Auliffe plots were more likely to yield interpretable ordination results, even though they included only the perennial flora.
Tree seedling development in tropical dry abandoned pasture and secondary forest in Costa Rica
Authors: Gerhardt Karin 
Published: May 2006

AbstractDevelopment of planted seedlings of four canopy tree species in recently abandoned pastures (mown and unmown) and in ca. 40‐yr old secondary dry forest in Guana‐caste National Park, Costa Rica, was studied from July 1989–June 1992. The species were the light‐demanding Cedrela odorata and Swietenia macrophylla, and the shade‐tolerant Hymenaea courbaril and Manilkara chicle. Seedling mortality was high and primarily correlated with dry season drought. After the first dry season, M. chicle and C. odorata showed < 5 % survival in the pasture and 20 % in the forest, but after 3 yr survival had decreased to 3% in all plots. Survival of S. macrophylla was highest in the mown pasture (45 % after 3 yr) and lowest in the forest (10 %). For H. courbaril, survival was 40–55 % under all three conditions.Growth rates were low, with a height increment of < 15 cm/yr, possibly due to low precipitation in 1990 and 1991. All species grew taller in the pasture than in the forest.Differences in soil depth, texture and drainage appeared to contribute to variation in the results both within and between plots. Herbivory contributed to the lower survival of C. odorata and S. macrophylla in the forest.
Fine‐grain pattern in Southern Cape plateau forests
Authors: Midgley J. , Seydack A. , Reynell D. , McKelly D. 
Published: May 2006

Abstract. Regeneration levels, size class distributions and a nearest neighbour technique were used to describe apreliminary dynamics frameworkfortheplateauforests. Taken over a large area, most of the canopy dominants have a negative exponential distribution of stems > 10 cm dbh per size class. In small (0.04 ha) plots, if present as more than one stem, most species are present as both canopy (> 25 cm dbh) and understorey (10–15 cm dbh) individuals. The canopy dominants maintain their rank in the bank of advance regeneration (> 5 cm height < 10 cm dbh). However, relative numbers of all regeneration of most canopy individuals are not strongly correlated with canopy closure or local abundance of conspecific adults. The mean area of nearest neighbour polygons of canopy individuals around saplings of the more common species are small.In conclusion, most species appearto be shade tolerant and locally persistent conferring a fine grain on this forest. We support recent questioning of universality of the gaps/non gaps paradigm.
Nutrient utilization in Quercus leucotrichophora and Pinus roxburghii seedlings at five soil fertility levels
Authors: Singh S. P. , Bisht Kiran 
Published: May 2006

Abstract. Nutrient utilization and growth performance of Pinus roxburghii Sarg. and Quercus leucotrichophora A. Camus, the two major forest trees of the Central Himalaya Mountains between 1000 and 2000 m elevation, were analysed at different nutrient levels. The early successional P. roxburghii occurs naturally on nutrient‐poor sites and the late successional Q. leucotrichophora on nutrient‐rich sites. Seedlings of these two species were grown both in monoculture and mixed, in plastic bags containing 1 kg soil and representing five levels of nutrients (NPK) in a 12 : 32 : 16 ratio.The P. roxburghii seedlings showed significantly greater nutrient extraction efficiency (nutrient unit extracted by seedlings per nutrient unit in the soil) than the Q. leucotrichophora seedlings, and this difference was increased in interspecific competition, particularly at the higher nutrient levels. In interspecific competition the extraction efficiencies of P. roxburghii for N, P and K were distinctly higher than those of Q. leucotrichophora. This we consider to be the main reason for the replacement of Q. leucotrichophora by P. roxburghii, even on nutrient‐rich soils, after disturbance and subsequent increase in light availability. In both the species, re‐translocation of nutrients from senescing leaves declined with increasing soil fertility. For example, re‐translocation for P. roxburghii was 49% N, 30% P and 32% K at the lowest soil fertility, and 20% N, 8% P and 13% K at the highest soil fertility.
Elevational distribution of conifer‐broadleaved hardwood forests on South Island, New Zealand
Authors: Allen Robert B. , Reif A. , Hall G. M. J. 
Published: May 2006

AbstractConstrained canonical correspondence analysis was used to compare the elevational distribution of conifer‐broadleaved hardwood forests at nine localities on South Island, New Zealand. Elevations of individual species were compared using cover‐weighted mean elevations and cover‐weighted standard deviations of mean elevation. Mean elevations of floristically similar stands declined with latitude, but was also lower at a locality with a granite substrate than at an adjacent locality with a schist substrate. The mean elevation breadth of frequent species (those in >5% of stands) was greatest at a locality underlain by schist and least at a locality underlain by granite. This is consistent with wide habitat breadth for species in early successional stages, because forest underlain by schist is more frequently disturbed than forest underlain by granite. Elevation breadth of frequent species was less, and species' turnover greater, in South Island conifer‐broadleaved hardwood forests than in conifer forests at similar latitudes in the Southern Rocky Mountains, USA.
Gap structure, disturbance and regeneration in a primeval Picea abies forest
Authors: Liu Qinghong , Hytteborn Hakan 
Published: May 2006

AbstractWe investigated patterns of disturbance and recovery in Fiby urskog, a primeval spruce (Picea abies) forest, situated south of the border between the Boreo‐nemoral and Boreal regions in East‐central Sweden. The main types of disturbances are storm damage, fungal infection and insect attacks. The response of the different tree species varied and the mode of tree‐fall depended on the different combinations of disturbance agents. The DBH distributions of gap creators and gap‐border trees were almost the same. There was a high age diversity (100–240 yr) among the fallen trees. We concluded that all canopy trees (DBH > 20 cm) had the same probability of being felled by storms, irrespective of their age and DBH.According to an estimate along transect lines, gaps made up 31% of the spruce forest area. Individual gap sizes ranged from 9 m2 to 360 m2, but 83% of the gaps were < 150 m2. The varied age structure of logs in individual gaps indicated that gap enlargements were common. 96 tree‐falls were observed on four days with an hourly mean wind speed > 12.0 m/s; all trees fell in the direction of the wind. However, when we consult the 30‐yrrecord(l 959–1989)ofthemeanhourly wind speed >12.0 m/s, it is clear that the pattern of storm‐directions does not match the pattern of orientation of fallen logs.The present disturbance regime and the predominance of small gaps were more favourable for the regeneration oí Picea abies than of light‐demanding tree species. In one large, 2900 m2 gap, not crossed by the transects, all the major tree species had established within 7 yr, suggesting that classical succession in the sense of complete species replacement or ‘relay floristics’ didnot occur. Our observations seem rather to fit the ‘initial floristic’ model. Estimates of turnover time ranged from 170 to 228 yr, depending on the method used.
Forest gap formation and closure along an altitudinal gradient in Tongariro National Park, New Zealand
Authors: Ogden J. , Fordham R. A. , Pilkington S. , Serra R. G. 
Published: May 2006

Abstract24 treefall gaps accumulated over a 10 year period along an altitudinal transectcovering 4.6ha on Mt. Hauhungatahi, Tongariro National Park, New Zealand were described quantitatively in terms of the area of damage (‘expanded gap’), the canopy opening (‘Tight‐gap’) and the size of the root mound. Tree mortality and branch loss following cyclone Bola, 1988, were recorded. In each gap saplings were ranked by species according to their vigour. Pre‐gap and post‐gap vertical and horizontal branch growth rates were calculated. Effects in the subalpine forest (> 1050 m) were compared with those in the montane zone.Tree mortality was highly episodic, associated with major storms, and patchy. Falling canopy trees destroyed, on average, 1.3 additional trees (> 10 cm diameter at 1 m). About half the trees were uprooted and the remainder broken off. Uprooted angiosperm (canopy) trees frequently resprouted from their bases, gymnosperms rarely. Expanded gap area averaged 56 m2 in the sub‐alpine forest and 88 m2 in the montane zone. Median expanded gap areas were about twice those of light gaps. Gap size frequency distribution was highly skewed. The largest gap was formed by a single Dacrydium cupressinum which destroyed six other trees creating a gap of ca. 0.03 ha.Expanded gaps, light gaps, and root mounds comprised 4.5, 2.8 and 0.1 % of the forest area in the sub‐alpine zone, and 3.8, 2.5 and 0.06 % in the montane forest. These values represent 10 years of accumulation, and imply light gap ‘return times’ of 360 years for the sub‐alpine and 400 years for the montane forest. These periods are in agreement with the known longevities of the canopy and emergent trees.Vertical shoot growth rate was about twice that in the horizontal plane, and both increased following gap formation. The relative increase was greatest in the subalpine forest. Using the measured growth rates it is estimated that gaps of median dimensions are filled by lateral extension growth in 31–44 yr. Saplings require longer to reach the mean canopy height and consequently require large (multiple tree) gaps or sequential gap events.
A method for studying dead bole dynamics in Pinus contorta var. latifolia ‐ Picea engelmannii forests
Authors: Johnson E. A. , Greene D. F. 
Published: May 2006

Rates of decomposition were determined for the boles of Pinus contorta var. latifolia Engelm. and Picea engelmannii Parry ex. Engelm. in five lower subalpine forest stands in the Southern Canadian Rocky Mountains. Stands ranged in age from 58 to 222 yr since last fire. The date of death of standing dead and fallen boles was determined by cross‐dating their ring‐width patterns to stand master ring‐ width chronologies. Boles could be dated which had been dead for up to 35 years in a 58‐yr old stand and 100 yr in a 222‐yr old stand.An empirical relationship between mass density and diameter of live trees was used to predict the mass density at death for trees already dead. The falling rate of dead standing boles was estimated from the dead bole's time of death and whether it was standing or on the ground at the time of observation. The falling rates for both Pinus contorta and Picea engelmannii ranged from 0.020 to 0.064/yr falling with most stands in the 0.050 range. No effect of size was found on the falling rate probably as a result of the small size of the boles (< 20 cm). Because of their dry condition standing dead boles do not decompose.An equation was developed which estimates the time a dead bole has been on the ground, given that it would have stood for some time before falling over and been subject to little decomposition during this time. Decomposition rates, using a negative exponential model, gave only marginally better r2 than linear models. Pinus contorta had exponential decay rates from 0.0299 and 0.0171 mass density loss/yr for the most recent 15 and 25 yr in stands 58 yr old, to 0.0045 and 0.0035 mass loss/yr for the most recent 65 and 80 yr in stands 215 and 222 yr old. Picea engelmannii had exponential decay rates of 0.0054 and 0.0025 mass loss/yr for the most recent 20 and 65 yr in stands 99 and 215 yr old.
The effect of salinity on the dominance‐diversity relations of experimental coastal macrophyte communities
Authors: Grillas Patrick , van Wijck Carla , Bonis Anne 
Published: May 2006

AbstractSalinity and water regime have previously been recognised as the main environmental factors controlling the abundance of coastal submerged macrophytes in temporarily‐flooded marshes in the Camargue. The effects of these environmental variables, which are considered interrelated, are tested experimentally by subjecting experimental macrophyte communities from six temporarily flooded marshes to different levels of salinity (from 0 to 6 g/1 Cl−). Communities subjected to high salinity levels (4 and 6 g/1 Cl~) showed a decrease in species richness and in biomass of all species involved. The species that most frequently dominate these communities, Chara áspera and Zannichellia pedunculata, are tolerant of salt and dominate over the entire salinity range. Three species groups can be distinguished based on the distribution of their biomass and centre of gravity of distribution over the salinity range: (1) non‐salt‐tolerant species, ‘glyco‐phytes’, (2) moderately salt‐tolerant species and (3) very tolerant species (‘halophytes’). A species ordination based on the experiments appeared to give results close to those previously obtained from field data.
A vegetation switch as the cause of a forest/mire ecotone in New Zealand
Authors: Agnew A. D. Q. , Wilson J. Bastow , Sykes Martin T. 
Published: May 2006

Abstract. Vegetation switches are those processes in which there is positive‐feedback between vegetation and environment, i.e. a vegetation state modifies its environment producing conditions more favourable to itself (Wilson & Agnew 1992). Switches can produce and maintain abrupt ecotones between plant communities.Such a sharp ecotone exists between beech‐podocarp forest and mire vegetation, both on deep peat, in southwest New Zealand. One such site was examined. There was no apparent explanation for the ecotone in the present topography nor in the substrate.Levelled transects through the forest demonstrated that most seedling establishment occurred on dead fallen tree boles. These microsites were significantly richer in N, P and K than the wet sump microsites. We argue that this is a mechanism whereby trees can become established in the forest, but not in the open mire. In the forest, the presence of trees ensures the presence of dead‐log microsites on the ground, permitting tree seedlings to grow. In the mire, there are no such micro‐sites, and trees cannot establish.The ecotone may be sharpened because of the presence of an ecotonal band of the small tree Leptospermum sco‐parium between forest and mire. This species can reproduce vegetatively by root suckers in the mire. Its boles are light, and even if they fall to the mire surface they are not thick enough to form a substrate for tree‐seedling establishment. The larger tree species may be prevented from falling onto the mire by the wind‐sheltering of the forest, and by the zone of Leptospermum.The postulated process would represent a new kind of water‐/nutrient‐mediated switch, of Type 1 (‘One‐sided’). It may occur in many waterlogged forests worldwide.
Structure and seasonal dynamics of humid tropical grasslands in Meghalaya, India
Authors: Shankar Uma , Tripathi R. S. , Pandey H. N. 
Published: May 2006

Abstract. Four humid grassland communities at three different locations in Meghalaya, India were analysed during 1988 and 1989 for species and life‐form composition, diversity and dominance in relation to altitude, soil and prevailing disturbances. Due to the adverse interactive influences of exceptionally high annual rainfall (> 10 000 mm), topography and human interference on soil fertility, the grassland at Cherrapunji, at 1300 m altitude, had a low species diversity (H'= 1.74) and was dominated by three perennial grass species. Similar grasslands, at both higher and lower altitudes on fertile soil and with lower rainfall (ca. 2000 mm), showed higher diversity values (H'= 2.28 at Burnihat and 2.31 at Upper Shillong). The proportion of perennial species and chamaephytes increased with elevation. At the high altitude site a grassland under short‐term protection from fires and grazing had a higher species richness, density and basal cover than an unprotected grassland. All grasslands show a clear seasonality, albeit with different patterns, with a maximum in density and basal cover in August.The differences in structure and seasonality are discussed in terms of different levels of stress.
Nitrate reductase activity in vegetation below an arctic bird cliff, Svalbard, Norway
Authors: Odasz Ann Marie 
Published: May 2006

Abstract. Vegetated sites below bird‐nesting cliffs are uniquely nutrient‐rich habitats in the otherwise nutrient‐poor arctic environment. Plants from six distinct vegetation zones below such a cliff at 79° N, Svalbard, Norway, were collected for analysis under greenhouse conditions. Leaf nitrate reductase activity (NRA) was analysed in 42 species representing 25 % of the Svalbard vascular flora. The species mean NRA values ranged from 0.37 to 8.34 μmols of nitrite ions formed per gram of plant fresh weight per hour. Species in the vegetated zone growing closest to recent guano deposits had the highest NRA values, (mean = 4.47) whereas plants growing farther below the cliff had significantly lower values (mean = 0.55).A similar pattern was detected in a duplicate set of plants induced with 15 mM KNO3; vegetation zone means for NRA ranged from 5.08 to 0.98 μmols of nitrite ions formed per gram of plant fresh weight per hour. Maximally induced species NRA values were highest in the first zones below the cliff and decreased downslope. This gradient paralleled the steep soil nitrate gradient, which decreased from 13.84 mg/l at the cliffbase to 1.03 mg/l downslope. Correspondingly, soil ammonium ions in the vegetation zones ranged between 1.96 mg/l at the cliff‐base to 0.03 mg/l downslope. Correlations between NRA and soil nitrate provide a systematic basis for assigning scalar ‘nitrogen figures’ as indicators of habitat preference, here for the first time applied to arctic species.