Nurse-plant and mulching effects on three conifer species in a Mexican temperate forest

Nurse-plant effects have been used as an effective reforestation and restoration strategy, and mulching has also effectively ameliorated soil-adverse conditions. However, use of nurse plants is limited by the presence of suitable nurse species before trees are planted, and use of mulching depends on availability of appropriate materials. The effects of Lupinus elegans as a nurse plant and pine-bark mulch were tested on three conifer species: Pinus montezumae, Pinus pseudostrobus, and Abies religiosa. We tested if nurse-plant type effects occurred if the lupines and the conifers were planted simultaneously. Overall survival was 53%, and significant differences among species were found. Survival regardless of cover type was significantly higher (P < 0.01) for P. pseudostrobus 17-month-old seedlings at planting (81%), followed by P. montezumae 7-month-old seedlings at planting (71%), P. pseudostrobus 7-month-old seedlings at planting (42%) and finally A. religiosa 7-month-old seedlings at planting (17%) the differences among the treatments were significant (P < 0.01). As a soil shading agent, lupines had a significant effect (P = 0.02), because they increased survival of P. pseudostrobus and A. religiosa, the effect of mulching with pine bark was not significant. The effects of a shading agent on growth differed among species. In particular lupines reduced height and stem diameter for P. montezumae and P. pseudostrobus, between 22% and 33%, and had no effect on growth of A. religiosa. The positive effects of the simultaneous planting of L. elegans on the survival of the trees suggests that nurse-plant facilitation can be used in areas where no suitable nurse plants are already present.     

Colonization of Pinus halepensis in Mediterranean habitats: consequences of afforestation, grazing and fire

The expansion of P. halepensis from plantations into natural sites of high conservation value is becoming a frequent occurrence across the Mediterranean zone of Israel. We studied how colonization of Pinus halepensis in natural Mediterranean habitats is related to afforestation, cattle grazing and fire. The study was conducted in a Mediterranean garrigue (Shrubland) located in Ramat Hanadiv Nature Park, southern Mt. Carmel region, Israel. The study area (ca. 350 ha) was divided into cells (100 × 100 m) each of which was categorized with respect to distance from planted pines, grazing (grazed since 1990/ungrazed), fire (burned in 1980/unburned), and vegetation structure (garrigue, dense garrigue, dense woodland). The location of colonizing pines, typically three m or more in height, was determined using an aerial photograph. Density of colonizing pines decreased linearly with the distance from planted pines within 300 m from planted pines with a long tail that extended out to ca 1,000 m. Over 90% of the colonizing pines that were found were located within a distance of 300 m (56% of the park area) from planted pines. Colonization was about two times greater under grazing than without grazing. The effects of fire and of the interaction fire × grazing were found insignificant. A separate analysis reveled that colonization was about 2 times larger in patches of sparse woody cover than in those of dense cover. In conclusion, pine colonization was mainly determined by the proximity to seed sources. Additionally, pine colonization was enhanced by cattle grazing probably through reduction of the natural vegetation cover.     

Incorporating Restoration in Sustainable Forestry Management: Using Pine-Bark Mulch to Improve Native Species Establishment on Tephra Deposits

Native plant establishment is limited by harsh environmental conditions in areas affected by tephra deposition following volcanic eruptions. Late‐successional species might be lacking even decades after the disturbance. We assessed the effectiveness of pine‐bark mulch, a by‐product of sustainable timber production in the study area, in promoting the establishment and survival of a late‐successional species (Pinus pseudostrobus) and a nitrogen‐fixing legume (Lupinus elegans). We established a factorial experiment in areas covered with tephra during the eruption of the Paricutín volcano in the state of Michoacán, Mexico. After 1 year, P. pseudostrobus survival was significantly higher (p < 0.001) in plots with pine‐bark mulching (46.5%) than in plots without mulching (21.8%). After 2 years, surviving pines with mulching were significantly taller (p= 0.03) than pines without mulching (45.3 ± 3.8 cm and 31.2 ± 3.7 cm, respectively). Lupinus elegans plants survived longer when grown in plots with pine‐bark mulching than without mulching. Mulching reduced tephra temperatures during the dry season (when temperatures can reach up to 58°C 4 cm below the surface of bare tephra). Lupinus elegans plants were affected by herbivory by small rodents, run‐off, and frost at the end of the growing season. Our results suggest that mulching can ameliorate harsh environmental conditions on sites covered with tephra while incorporating a by‐product of sustainable forestry into restoration practice.     

Ontogenetic differentiation between Mediterranean and Eurasian pines (sect. Pinus) at the seedling stage

Heteroblastic development in pine seedlings includes extreme morphological changes with still unclear adaptive and evolutionary significance. In particular, Mediterranean and Eurasian pines (section Pinus) living in the Mediterranean basin seem to follow quite distinct developmental trajectories at the seedling stage. Aiming to confirm this ontogenetic differentiation we performed a nursery experiment with seedlings of five Mediterranean pines (Pinus pinaster, P. brutia, P. halepensis, P. pinea and P. canariensis) and three Eurasian pines (P. sylvestris, P. uncinata, and P. nigra subsp. salzmannii), also including P. radiata as an outgroup. After destructive analyses at two harvest times (9 and 32 weeks), we found sharp differentiation between Mediterranean and Eurasian pines in a combination of traits linked to shoot heteroblasty. In particular, Mediterranean pines showed a marked delay in the proportion of adult needles to total needles in the shoot compared to Eurasian species, especially at the second harvest. However, two Mediterranean pines, P. pinaster and P. brutia showed a slightly higher proportion of secondary needles, and a higher rate of budset at a more advanced stage (68 weeks) compared to the other three Mediterranean species. Meaningfully, the outgroup P. radiata was the only species combining a high proportion of adult foliage since the first harvest with a delayed formation of the first terminal bud. We discussed the adaptive significance of these findings at the light of species’ climatic niches and life histories.     

Damage of alpine vegetation by the 2009 fire on Mt. Shirouma, central Japan: comparison between herbaceous vegetation and Pinus pumila scrub

A fire occurred (0.59 ha) in an alpine fellfield (2600 m a.s.l.) on Mount Shirouma, central Japan, on 9 May 2009 before the start of the growing season. Herbaceous plants and dwarf pine Pinus pumila dominated the site. Plots were established in burned and unburned herb vegetation and P. pumila scrub just after the fire to monitor vegetation recovery. This study reports the short-term monitoring results 3 months after the fire. Burned herb vegetation mostly recovered by late August 2009. However, burned P. pumila did not recover, and other alpine plants were scarce in burned P. pumila scrub. The observed number of species in herb vegetation was 15–20 m⁻² whereas it was only 1–6 m⁻² in P. pumila scrub. The total cover of plants was 111–129% for burned herb vegetation but was only 8–31% for burned P. pumila scrub. Although the species composition in P. pumila scrub distinctly differed between burned and unburned plots, in herb vegetation it was similar between them. Therefore, P. pumila scrub was greatly damaged by the fire, whereas herb vegetation was not damaged. Rapid recovery of herbaceous plants was because winter buds in the soil were not damaged by the fire, but winter buds on shoots of P. pumila were burned. Therefore, the difference in winter bud location (above or belowground) may have resulted in the difference in damage between herbaceous plants and P. pumila.     

Phosphorus Translocation by Red Deer on a Subalpine Grassland in the Central European Alps

We examined the role of red deer (Cervus elaphus L.) in translocating phosphorus (P) from their preferred grazing sites (short-grass vegetation on subalpine grasslands) to their wider home range in a subalpine grassland ecosystem in the Central European Alps. Phosphorus was used because it is the limiting nutrient in these grasslands. When we compared P removal of aboveground biomass due to grazing with P input due to the deposit of feces on a grid of 268 cells (20 m × 20 m) covering the entire grassland, we detected distinct spatial patterns: the proportion of heavily grazed short-grass vegetation increased with increasing soil-P pool, suggesting that red deer preferably grazed on grid cells with a higher soil-P pool. Biomass consumption related to increased proportion of short-grass vegetation, and therefore P removal, increased with increasing soil-P pool. However, within the two vegetation types (short-grass and tall-grass), consumption was independent from soil-P pool. In addition, P input rates from defecation increased with increasing soil-P pool, resulting in a constant mean net P loss of 0.083 kg ha⁻¹ y⁻¹ (0.03%–0.07% of soil-P pool) independent of both soil-P pool and vegetation type. Thus, there was no P translocation between grid cells with different soil-P pools or between short-grass and tall-grass vegetation. Based on these results, it is likely that the net rate of P loss is too small to explain the observed changes in vegetation composition from tall-herb/meadow communities to short-grass and from tall-grass to short-grass on the grassland since 1917. Instead, we suggest that the grazing patterns of red deer directly induced succession from tall-herb/meadow communities to short-grass vegetation. Yet, it is also possible that long-term net soil-P losses indirectly drive plant succession from short-grass to tall-grass vegetation, because nutrient depletion could reduce grazing pressure in short-grass vegetation and enable the characteristic tall-grass species Carex sempervirens Vill. to establish.     

Mechanisms of Araucaria (Atlantic) Forest Expansion into Southern Brazilian Grasslands

Recent studies have shown that tropical and subtropical forests expanded during the late Holocene, but rates and mechanisms of expansion are still unknown. Here, we investigate how a forest–grassland mosaic changed over the past 10,000 years at the southernmost limit of the Brazilian Atlantic forest. We used soil organic matter carbon isotopes (δ¹³C and ¹⁴C) to quantify and date changes in vegetation, examining soil properties and leaf traits of tree species (nutrient content, δ¹³C, δ¹⁵N, and specific leaf area—SLA) to describe potential mechanisms of expansion. Our results show that after several millennia of stability, forests have been expanding over grasslands through continuous, but very slow, border dynamics and patch formation (<100 m since ~4,000 YBP). This process of expansion coincided with past changes in climate, but biotic feedback mechanisms also appear to be important for the long-term persistence and expansion of forests. Soil fertility and microbial biomass match current rather than past vegetation distribution, increasing progressively across the gradient: grasslands < isolated trees < forest patches < forests. Foliar δ¹⁵N values of trees that are able to colonize the grassland are consistently lower across this vegetation gradient, suggesting an increasingly greater reliance on symbiotic nutrient uptake from grasslands to forests. No significant relationships were found between soil and leaf nutrients, but SLA explained variation in leaf N, P, and K (positive relationships) and in leaf δ¹³C (negative relationship). These findings suggest that a tradeoff between tree growth and water use efficiency is an important regulator of forest–grassland dynamics in the study region.     

The Complementarity of Extractable and Ester-Bound Lipids in a Soil Profile Under Pine

Extractable and solvent insoluble, ester-bound lipids were analysed in an acid, sandy soil profile under Corsican pine. The n-alkanes and alkanoic acids from the soil profile showed rather poor correlations with those from the pine needles and roots, while the n-alkanol composition in the mineral horizons strongly indicated the presence of lipids derived from a previous grass vegetation. Although the ester-bound lipids (ω-hydroxyalkanoic acids and α,ω-alkanedioic acids (>C₂₄)) suggested that plant sources other than pines were present in the mineral soil horizons their composition was less contaminated and a clear distinction between needle and root input could be discerned. The divergent clustering of soil horizons and plant materials by individual and combined compound classes emphasized the usefulness of both extractable lipids and cutin/suberin in unravelling (past) vegetation and tissue history and contributions to soil organic matter.     

Is fire a selective force of seed size in pine species?

Fire is selectively shaping most of the traits of plants growing in fire-prone environments. However, seed size and other features related to seed production have not been studied in the light of the evolutionary role of fire. Our research tests the hypothesis that larger seeds have a higher chance of surviving wildfires and produce more vigorous seedlings with a lower death rate. To test this hypothesis the germination and early seedling growth of five Spanish pine species were studied. Weight, length and width of all seeds were measured. The biomass (fresh and dry weight) and length (root and total) of subsequent seedlings were also measured after 30 d from emergence. Seeds were submitted to elevated temperatures for periods in which the chance of survival was 50 % (calculated by means of a logistic model for each pine species). The differences observed among species suggests that fire may be adaptively shaping seed size in pines with larger seeds (Pinus canariensis and P. pinaster), because larger seeds are more likely to survive after heat shocks. Furthermore, in P. canariensis, seedlings after heat treatment are even larger than those submitted to control. In P. halepensis, despite being well adapted to fire, our results indicated no relationships between fire and seed characteristics. Finally, although heat treatment has a general adverse effect on seedling growth in the case of the two subalpine pines, we have detected a positive relationship between seed size and seedling growth but only in the largest seeds. This might also suggest the relevance of fire as a selective force for these pines which is outperformed by the relevance of dispersal and emergence time as adaptive traits in the post-fire scenario.     

How did climate drying reduce ecosystem carbon storage in the forest–steppe ecotone? A case study in Inner Mongolia, China

The projected recession of forests in the forest–steppe ecotone under projected climate drying would restrict the carbon sink function of terrestrial ecosystems. Previous studies have shown that the forest–steppe ecotone in the southeastern Inner Mongolia Plateau originally resulted from climate drying and vegetation shifts during the mid- to late-Holocene, but the interrelated processes of changing soil carbon storage and vegetation and soil shifts remain unclear. A total of 44 forest soil profiles and 40 steppe soil profiles were excavated to determine soil carbon storage in deciduous broadleaf forests (DBF), coniferous forests (CF) and steppe (ST) in this area. Carbon density was estimated to be 106.51 t/hm² (DBF), 73.20 t/hm² (CF), and 28.14 t/hm² (ST) for these ecosystems. Soil organic carbon (SOC) content was negatively correlated with sand content (R = −0.879, P < 0.01, n = 42), and positively correlated with silt (R = 0.881, P < 0.01, n = 42) and clay (R = 0.858, P < 0.01, n = 42) content. Consistent trends between fractions of coarse sand and a proxy index of relative aridity in sediment sequences from two palaeo-lakes further imply that climate drying reduced SOC through coarsening of the soil texture in the forest–steppe ecotone. Changes in carbon storage caused by climate drying can be divided into two stages: (1) carbon storage of the ecosystem was reduced to 68.7%, mostly by soil coarsening when DBF were replaced by CF at ~5,900 ¹⁴C years before present (BP); and (2) carbon storage was reduced to 26.4%, mostly by vegetation shifts when CF were replaced by ST at ~2,900 ¹⁴C years BP.     

Effects of mixing pine and broadleaved tree/shrub litter on decomposition and N dynamics in laboratory microcosms

This study was carried out to compare the ecological function of exotic pine (Pinus radiata—Pr) and native pine (Pinus tabulaeformis—Pt) in terms of litter decomposition and its related N dynamics and to evaluate if the presence of broad-leaved tree species (Cercidiphyllum japonicum—Cj) or shrub species (Ostryopsis davidiana—Od) litter would promote the decomposition of pine needles and N cycling. Mass remaining, N release of the four single-species litters and mixed-species (Pt + Cj; Pr + Cj; Pt + Od; Pr + Od) litters and soil N dynamics were measured at microcosm scale during an 84-day incubation period. The Pt and Pr litter, with poorer substrate quality, indicated slower decomposition rates than did the Cj and Od litter. Due to their high C/N ratios, the N mass of Pt and Pr litter continuously increased during the early stage of decomposition, which showed that Pt and Pr litter immobilized exogenous N by microbes. No significant differences of soil inorganic, dissolved organic and microbial biomass N were found between the Pt and Pr microcosm at each sampling. The results showed that the exotic Pr performed similar ecological function to the native Pt in terms of litter decomposition and N dynamics during the early stage. The presence of Cj or Od litter increased the decomposition rates of pine needle litter and also dramatically increased soil N availability. So it is feasible for plantation managers to consider the use of Cj as an ameliorative species or to retain Od in pine plantations to promote the decomposition of pine litter and increase nutrient circulation. The results also suggested that different species litters induced different soil dissolved organic nitrogen (DON). As a major soluble N pool in soil, DON developed a different changing tendency over time compared with inorganic N, and should be included into soil N dynamic under the condition of our study.     

Aboveground net production and dry matter allocation ofPinus pumila forests in the Kiso mountain range,central Japan

Aboveground net production rates of the subalpine stone pine (Pinus pumila) forests in central Japan were estimated by the summation method; net production was defined as the sum of annual biomass increment and annual loss due to death. In the two pine stands of different scrub heights, P1 (200 cm) and P2 (140 cm), aboveground biomass reached 177 and 126 ton ha⁻¹, respectively. Leaf biomass was about 14 ton ha⁻¹ in each stand. The estimates of aboveground net production during the 2 year period (1987–1989) averaged 4.1 and 3.7 ton ha⁻¹ y⁻¹ in P1 and P2, respectively, which were at the lowest among the pine forests in the world. Two indices of efficiency of energy fixation, that is, the ratio of net production to the total radiation during a growing season and the ratio of net production to total radiation per unit of leaf weight, were evaluated. Both efficiency indices for the twoP. pumila stands fell in the range obtained for other Japanese evergreen conifer forests. This suggested that the low annual net production of the stone pine stands were mainly due to a limitation in the length of the growing season. The pine forests were also characterized by a small allocation (about 17%) of aboveground net production into biomass increment, in comparison with other evergreen conifer forest types. Annual net carbon gain in theP. pumila forests was suggested to be largely invested in leaf production at the expense of the growth of woody parts.     

The complete mitochondrial genome structure of snow leopard <Emphasis Type="Italic">Panthera uncia</Emphasis>

The complete mitochondrial genome (mtDNA) of snow leopard Panthera uncia was obtained by using the polymerase chain reaction (PCR) technique based on the PCR fragments of 30 primers we designed. The entire mtDNA sequence was 16 773 base pairs (bp) in length, and the base composition was: A—5,357 bp (31.9%); C—4,444 bp (26.5%); G—2,428 bp (14.5%); T—4,544 bp (27.1%). The structural characteristics [0] of the P. uncia mitochondrial genome were highly similar to these of Felis catus, Acinonyx jubatus, Neofelis nebulosa and other mammals. However, we found several distinctive features of the mitochondrial genome of Panthera unica. First, the termination codon of COIII was TAA, which differed from those of F. catus, A. jubatus and N. nebulosa. Second, tRNA^{Ser (AGY)}, which lacked the ‘‘DHU’’ arm, could not be folded into the typical cloverleaf-shaped structure. Third, in the control region, a long repetitive sequence in RS-2 (32 bp) region was found with 2 repeats while one short repetitive segment (9 bp) was found with 15 repeats in the RS-3 region. We performed phylogenetic analysis based on a 3 816 bp concatenated sequence of 12S rRNA, 16S rRNA, ND2, ND4, ND5, Cyt b and ATP8 for P. uncia and other related species, the result indicated that P. uncia and P. leo were the sister species, which was different from the previous findings.     

The role of below-ground competition during early stages of secondary succession: the case of 3-year-old Scots pine (Pinus sylvestris L.) seedlings in an abandoned grassland

In abandoned or extensively managed grasslands, the mechanisms involved in pioneer tree species success are not fully explained. Resource competition among plants and microclimate modifications have been emphasised as possible mechanisms to explain variation of survivorship and growth. In this study, we evaluated a number of mechanisms that may lead to successful survival and growth of seedlings of a pioneer tree species (Pinus sylvestris) in a grass-dominated grassland. Three-year-old Scots pines were planted in an extensively managed grassland of the French Massif Central and for 2 years were either maintained in bare soil or subjected to aerial and below-ground interactions induced by grass vegetation. Soil temperatures were slightly higher in bare soil than under the grass vegetation, but not to an extent explaining pine growth differences. The tall grass canopy reduced light transmission by 77% at ground level and by 20% in the upper part of Scots pine seedlings. Grass vegetation presence also significantly decreased soil volumetric water content (Hv) and soil nitrate in spring and in summer. In these conditions, the average tree height was reduced by 5% compared to trees grown in bare soil, and plant biomass was reduced by 85%. Scots pine intrinsic water-use efficiency (A/g), measured by leaf gas-exchange, increased when Hv decreased owing to a rapid decline of stomatal conductance (g). This result was also confirmed by δ ¹³C analyses of needles. A summer ¹⁵N labelling of seedlings and grass vegetation confirmed the higher NO₃ capture capacity of grass vegetation in comparison with Scots pine seedlings. Our results provide evidence that the seedlings' success was linked to tolerance of below-ground resource depletion (particularly water) induced by grass vegetation based on morphological and physiological plasticity as well as to resource conservation.     

Growth and nutritional response of Pinus pinaster after a large pine weevil (Hylobius abietis) attack

Hylobius abietis is an important pest of coniferous plantations in Europe, to which high mortality, stem deformities, and growth loss are typically attributed. In pine trees, as in other long-lived organisms, there is uncertainty regarding the long-term costs of short-term resistance against invading organisms. We examined the nutritional status of Pinus pinaster after a 2-year long H. abietis attack, measuring needle and phloem N and P concentrations, and the impact of the damage on subsequent growth, survival, and stem deformities over a period of 5 years. The study sites were a P. pinaster family × fertilization trial, and a neighbouring twin trial with similar climate and soil characteristics that was not attacked. Growth losses after the H. abietis attack were important (up to 40%), but restricted to the first years after the attack. Five years after the attack, the annual height increment of pines in the attacked stand was not related to the initial damage suffered, and plants showed regular stems, normal leader dominance, and regular height after 5 years. These findings suggest strong compensatory growth in P. pinaster and indicate relatively high tolerance to the large pine weevil. Needle nutrient concentrations in the healthy stand were, as expected, significantly greater in experimentally fertilized plants, and they were linearly related to those in phloem showing equilibrated stoichiometry both for nitrogen (r = 0.86; P < 0.01; N = 25) and phosphorus (r = 0.84; P < 0.01; N = 25). However, at the attacked stand, nutrient concentrations in the needles did not follow the experimentally manipulated nutrient availability in soils, and phosphorus concentration in the needles was unexpectedly not related to those in the phloem. The pine seedlings attacked by H. abietis showed altered potential of allocating nutrients to their tissues according to the nutrient availability existing in the soil, as well as altered stoichiometry in N and P concentrations among phloem and leaves. Maritime pine seems to be tolerant to the pine weevil attack, at least in the conditions of this study, where pine weevil damage caused a deep alteration of nutrient allocation and nutritional status. Further research is needed to elucidate to what extent altered nutrient allocation may be part of an induced response to the attack or just derived from the vascular injury caused by the weevil wounding in the phloem.     

Effects of climate, tree age, dominance and growth on δ15N in young pinewoods

Needles, annual rings from basal stem discs and bark of three dominant and three suppressed Pinus pinaster from a 12-year-old pine stand (naturally regenerated after a wildfire) were analysed to study the effects of climate, tree age, dominance, and growth on tree δ¹⁵N. Foliar-N concentration in dominant pines (0.780–1.474% N) suggested that soil N availability was sufficient, a circumstance that allowed isotopic discrimination by plants and (greater) differences in δ¹⁵N among trees. The δ¹⁵N decreases in the order wood (−0.20 to +6.12‰), bark (−1.84 to +1.85‰) and needles (−2.13 to +0.77‰). In all trees, before dominance establishment (years 1–8), the N stored in each ring displayed a decreasing δ¹⁵N tendency as the tree grows, which is mainly due to a more “closed” N cycle or an increasing importance of N sources with lower δ¹⁵N. After dominance establishment (years 9–12), wood δ¹⁵N values were higher in suppressed than in dominant trees (2.62 and 1.46‰, respectively; P < 0.01) while the reverse was true for needles and bark; simultaneously, the absolute amount of N stored by suppressed pines in successive rings decreased, suggesting a lower soil N assimilation. These results could be explained by lignification acting as major N source for needles in suppressed pines because products released and reallocated during lignification are ¹⁵N-depleted compared with the source. According to principal component analysis, wood δ¹⁵N appears associated with wood N concentration and precipitation during the growing season, but clearly opposed to age, basal area increment and mean temperature in spring and summer.     

Ground-dwelling predators can affect within-field pest insect emergence in winter oilseed rape fields

We investigated, (i) whether the emergence from pupation of two coleopteran pest insect groups in oilseed rape (OSR, Brassica napus L.)—pollen beetles (Meligethes spp. F., Nitidulidae) and stem weevils (Ceutorhynchus pallidactylus Marsh and C. napi Gyll., Curculionidae)—is affected by the exclusion of ground-dwelling predatory arthropods, and (ii) the role for pest control of the widely abundant carabid beetles Anchomenus dorsalis Pontop. and Poecilus cupreus L. Densities of ground-dwelling arthropods were manipulated using enclosures; emerging pest adults were assessed using emergence traps. Where arthropods had been excluded, between two (June sampling) and tenfold (August sampling) more stem weevils emerged than where predators had free access. The addition of 25 adult A. dorsalis m⁻² to formerly predator-free enclosures showed similar stem weevil emergence than plots where predators had free access; the addition of 25 adult P. cupreus m⁻² did not reduce stem weevil emergence. In August, both A. dorsalis and P. cupreus additions marginally significantly reduced pollen beetle emergence. Handling editor: Patrick De Clercq.     

The effects of reindeer grazing on the composition and species richness of vegetation in forest–tundra ecotone

We conducted an 8-year exclosure experiment (1999–2006) in a forest–tundra ecotonal area in northwestern Finnish Lapland to study the effects of reindeer grazing on vegetation in habitats of variable productivity and microhabitat structure. The experimental sites included tundra heath, frost heath and riparian habitats, and the two latter habitats were characterized by hummock-hollow ground forms. The total cover of vegetation, cover of willow (Salix spp.), dwarf birch (Betula nana), dwarf shrubs, forbs and grasses (Poaceae spp.) increased in exclosures in all habitats. The increase in the total cover of vegetation and in the covers of willow and dwarf birch tended to be greatest in the least productive tundra heath. Opposing to the increase in the dominant vascular plant groups, the cover and species number of bryophytes decreased in exclosures. We conclude that the effects of reindeer grazing on vegetation composition depend on environmental heterogeneity and the responses vary among plant groups. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The interplay of disturbance,vegetation structure,and propagule pressure contributes to Pinus kesiya invasion in Tapia woodland,Madagascar

Pinus are among the highly invasive species that have spread outside their plantation area after their introduction in the Southern Hemisphere. The case of Pinus kesiya invasion is observed in the high plateau of Madagascar, inside the sclerophyll Tapia woodland which is dominated by the endemic Uapaca bojeri tree species. The analysis of this invasion was carried out using 375 plots of 100 m² each in Tapia woodland. Data on the vegetation structure, the plot characteristics and the propagule pressure were collected. We recorded a total of 740 pines distributed in 29.8% of the plots. The generalized linear model built on P. kesiya at the three different life stages allowed us to highlight a different explicative variable on the species’ presence and abundance separately. The factors explaining pine occurrence varied according to the pine life stage. In the seedling stage, the distance of the plot from the propagule source combined with the longitudinal position of the plot explained 18% of the pine presence. In the sapling and adult stages, the vegetation structure was the main important factor (22% and 11% of variation explained regarding presence and abundance). The frequency of U. bojeri and the degree of disturbance were the most important factors characterizing this vegetation structure. Based on these results, a strategy to control pine invasion in the Tapia woodland may focus on enrichment with U. bojeri and limitation of the plantation of P. kesiya in proximity.