Comparative performance of the cotton bollworm,Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on various host plants

The effect of various host plants; chickpea (varieties Arman, Hashem, Azad and Binivich), bean varieties (Phaseolus vulgaris L.), common bean (Khomein), white kidney bean (Dehghan), red kidney bean (Goli), cowpea (variety Mashhad) and tomato (variety Meshkin) on the life table parameters of the cotton bollworm, Helicoverpa armigera (Hübner) were evaluated under laboratory conditions (25 ± 1 °C, 65 ± 5 % RH and a 16:8 h light:dark photoperiod). Records for larval period, pupal period, and development time of H. armigera were longest on tomato (24.9, 15.1, and 45.4 days, respectively) and shortest on chickpea Arman (17.5, 9.1, and 31.7 days, respectively). Among various host plants fecundity (total number of eggs laid per female) was highest (2,665 eggs) on chickpea Arman and the lowest (700 eggs) on tomato. The net reproductive rate (R ₀) was significantly affected by various host plants being highest on chickpea Arman (1,422) and lowest on tomato (111.3 females/female/generation). The highest and lowest intrinsic rates of natural increase (r _m) were observed on chickpea Arman (0.244 day^?1) and tomato (0.123 day^?1) varieties, respectively. Cluster analysis of the life table parameters of H. armigera on various host plants indicated that tomato, in comparison to other plants was an unsuitable host to H. armigera.     

Shade acclimation in the forage grass Festuca Pallescens: biomass allocation and foliage orientation

Plants can acclimate to shade through different processes. In particular, they can modify their biomass allocation and the architecture in order to increase light interception. The objective of this study was to evaluate the shade acclimation capacity of Festuca pallescens (St. Ives) Parodi, as part of research concerning the use of this species in silvopastoral systems in Patagonia, Argentina. Biomass allocation was estimated from the leaf and root dry weights of plants growing in an open pasture and forested plots. Crown architecture of plants growing in the open and in two shade treatments was studied dividing each plant in three concentric cylinders, within which leaf angles and leaf area were measured. Light interception of plants in each treatment was estimated from the projected leaf areas and the relative amount of radiation reaching each location. Biomass allocation changed significantly in plants growing under shade conditions, increasing the proportion of leaves relative to the roots (Leaf Mass Fraction = 0.29 (SD: 0.12) and 0.40 (SD: 0.09) in plants in the open and under shade, respectively). Also, mean leaf inclination angles changed in plants growing under shade conditions, allowing an increase in light interception of approximately 35% compared to plants with the crown architecture typical of the open treatment. Previous studies have shown that F. pallescens does not change its photosynthetic response to light under shade conditions. Therefore, we conclude that the reported changes in biomass allocation and crown architecture, in addition to the increment in specific leaf area explain the relatively high shade tolerance of this species. This revised version was published online in June 2006 with corrections to the Cover Date.     

Medicinal plants in old-growth, degraded and re-growth forests of NW Pakistan

Many old-growth forest stands in northwest Pakistan have been structurally transformed as a consequence of logging and livestock grazing, some of which are thereafter left to secondary succession. These forests represent an important resource for local inhabitants who gather and sell medicinal plants as part of their livelihood. With this in mind, the main objectives of our study were: (1) to assess differences in the structure of the tree layer and the abundance of medicinal plants among differently transformed forests, (2) to evaluate the recovery potential of medicinal plants under re-growth forests, and (3) to assess relationships between tree stand structural characteristics and the occurrence of medicinal plants.The first step of the study involved creating an approximate map covering an area of 90 km² for five forest-use types (old-growth forest, forest degraded by logging, derived woodland, agroforest and re-growth forest). Fifteen plots per forest-use type were randomly allocated at altitudes ranging from 2200 m to 2400 m asl, within which the abundance of 10 locally important medicinal herb species was assessed.The study stands differed greatly in tree basal area, which was highest in old-growth forest (48 m² ha⁻¹), lowest in agroforest areas (6 m² ha⁻¹) and intermediate in re-growth forest (20 m² ha⁻¹). All ten medicinal plant species were encountered in old-growth and in re-growth forests, but only five of these species also occurred on agroforest plots. The mean coverage of study medicinal plants was highest in old-growth forest (7%), low in forest degraded by logging, derived woodland and agroforest (0.3-2%), and intermediate in re-growth forest (4%). The Jaccard abundance based similarity index indicates a considerable similarity (0.6) between re-growth and old growth forest for both trees and medicinal plants. The overall abundance of medicinal plants increased with increasing tree basal area and canopy cover. The abundance of some particular species decreased; however, the most sought-after medicinal species Bergenia ciliata, Valeriana jatamansi and Viola cancescens increased with tree basal area within specific forest-use type and also across forest-use types. In conclusion, our data suggest that anthropogenic forest degradation leads to a reduction in the abundance of economically viable medicinal plants for the study region. It is further indicated that this can be reversed if degraded forests are allowed to regenerate.     

Reducing effect of an extract of Phaseolus vulgaris on food intake in mice — Focus on highly palatable foods

Different lines of experimental evidence indicate that treatment with extracts from and derivatives of Phaseolus vulgaris reduces intake of food, including highly palatable foods and beverages, in rats. The present study was designed to extend to mice these lines of evidence. To this end, CD1 mice were treated acutely with a standardized extract of P. vulgaris and then exposed to unlimited access to regular food pellets (Experiment 1) or 1-hour limited access to three different palatable foods/beverages, such as butter cookies (Experiment 2), a condensed-milk beverage (Experiment 3), and a chocolate-flavored beverage (Experiment 4). Treatment with P. vulgaris extract resulted in a significant reduction in the intake of regular food pellets, that was still evident 24 h later, as well as of the three palatable nourishments. Together, these results (a) extend to mice several previous findings on the capacity of P. vulgaris extracts to suppress food intake in rats, (b) suggest that P. vulgaris extracts may interfere with the central mechanisms regulating appetite, food intake, palatability, and/or the rewarding and hedonic properties of food, and (c) P. vulgaris extracts may represent a potentially effective therapy for overeating, obesity, and food craving.     

Possibilities of diverse rubber based agroforestry systems for smallholdings in India

Rubber growers in South East Asian countries are facing acute crisis due to the price volatility, sharp increase in cost of cultivation, increasing drought and declining soil fertility. With an objective to generate additional income and improve small-holder welfare by integrating diverse crops in rubber ecosystem, three experiments were conducted in Rubber Research Institute of India during 2001–2014 period. In one experiment, coffee, vanilla on Glyricidia standards, Garcinia and nutmeg were cultivated along with rubber without altering the planting design and density of rubber trees. Growth of rubber was significantly higher under mixed planting and yield was not influenced. Soil moisture status during summer and microbial population were higher in mixed planting system and soil nutrient status was maintained. Yield of all the intercrops was good during initial years. As the shade from rubber canopy intensified, Garcinia perished but vanilla and coffee continued to yield reasonably well. In another experiment, nine shade tolerant medicinal plants were evaluated in mature rubber plantation. All the medicinal plants established well and produced reasonable biomass, but the performance of Strobilanthes cuspida and Alpinia calcarata were comparatively better. In another study, it was observed that short duration vegetables like amaranthus and salad cucumber can be cultivated during the annual leaf shedding period in mature rubber plantations to meet part of the household requirement. The results showed that diverse crops can be integrated with rubber without any adverse effect on growth and yield of rubber. Crop diversification generated additional income, mitigated drought and sustained soil fertility.     

Silvicultural systems for plantation mahogany in Africa: Influences of canopy shade on tree growth and pest damage

Overexploitation of the African mahoganies, Khaya anthotheca and K. ivorensis, could lead to their commercial extinction in the near future. Efforts to establish plantations to sustain supply have been discouraged by the shoot borer Hypsipyla robusta Moore. We hypothesized that there is a shade level at which Hypsipyla attack and branching are reduced, but height growth is adequate. We report on the growth of these African mahoganies and Hypsipyla attack under three different forest canopy shade levels: open (55% open sky), medium shade (26% open), and deep shade (11% open). Hypsipyla attack on K. anthotheca was 85%, 11%, and 0% attack in the open, medium, and deep shade treatments, respectively. However, growth in medium and deep shade was slow. Mean tree height for K. anthotheca was 413.8, 126.2, and 54.5 cm in the open, medium and deep shade treatments, respectively. K. ivorensis showed similar trends. The reduced growth under these shade levels limit the use of this strategy for controlling Hypsipyla attack.     

Morphological plasticity and regeneration strategies of velvet leaf blueberry (Vaccinium myrtilloides Michx.) following canopy disturbance in boreal mixedwood forests

The effects of canopy disturbance on the abundance, growth, morphological plasticity, biomass allocation and fruit production of velvet leaf blueberry (Vaccinium myrtilloides Michx.) were examined in 1996 in a second-growth boreal mixedwood forest near Nipigon, northwestern Ontario that had been logged by either shelterwood cutting or clearcutting in 1993. We found that V. myrtilloides was able to persist in both open and closed canopy boreal mixedwood forests managed for commercial timber extraction. Persistence under heavy shade conditions was accompanied by significant morphological and biomass allocation plasticity. Specific leaf area, leaf area, individual leaf weight, and the proportion of total biomass in stems and foliage changed along an understory light gradient from 0% to 67% percent photosynthetic photon flux density (% PPFD). The degree of above-ground morphological plasticity may explain blueberry's ability to survive under low light conditions. Reproductive performance of V. myrtilloides was greatest under the partial shade conditions associated with shelterwood cutting. Blueberry bushes growing in clearcuts overgrown with 3-year old aspen (Populous tremuloides Michx.) saplings remained mostly vegetative whereas the number, fresh weight and dry weight of berries in shelterwood cuts was 94% grater than that produced after clearcutting. We attributed the lower fruit yields in the clearcuts to heavy shading from regenerating hardwoods, and mechanical damage to above-ground biomass. The paucity of seedling regeneration as well as extensive mechanical damage to above-ground stems by logging equipment delayed vegetative regeneration of V. myrtilloides in large canopy openings of the clearcut blocks. Unlike other more aggressive ericaceous species (e.g. Kalmia angustifolia var. angustifolia L., Gaultheria shallon Pursh.), V. myrtilloides was unable to resist invasion from faster growing hardwood species (e.g. P. tremuloides) and was rapidly overtopped. V. myrtilloides plants in the uncut control blocks received 3.9% of full sunlight, whereas those growing in the partial cut and clearcut blocks received an average of 25.3% and 32.5% PPFD, respectively. Cover of vegetation over-topping blueberry plants was highest in the uncut forest (90.3%), but was not significantly different between the partial cut (45.5%) and clearcut (50.1%) treatment blocks.     

Effect of root competition and shade on survival and growth of nine woody plant taxa within a pecan [Carya illinoinensis (Wangenh.) C. Koch] alley cropping system

Suitability for production of woody floral stems in a pecan [Carya illinoinensis (Wangenh.) C. Koch] alley cropping was determined for nine shrub species in northwest Florida. Treatments included partial shade without root competition, partial shade with root competition, and full sun. Only three species had high rates of survival for all treatments throughout both years of the study: Callicarpa americana L. (American beautyberry), C. americana var. Lactea (white American beautyberry), and Crataegus marshallii Eggl. (parsley haw). For C. americana, plant growth index increased through time and was similar among the three treatments, indicating that this species grew equally well in sun or shade irrespective of root competition from the tree crop. C. americana var. Lactea had similarly high rates of survival and grew largest in partial shade without root competition (81.7?cm) compared to partial shade with root competition (67.2?cm) and full sun (57.0?cm). C. marshallii had 100 % survival in partial shade without root competition, with one mortality in partial shade with root competition (91.7 % survival) and one in full sun (91.7 % survival). Growth index did not increase over time and was similar among all three treatments. Other species tested had low rates of survival in all treatments throughout both years of the study and included: Ilex glabra L. (inkberry), Ilex myrtifolia Walt. (myrtle-leaf holly), Hydrangea paniculata Seibold var. ??Tardiva?? (panicle hydrangea), Hydrangea quercifolia Bart. (oakleaf hydrangea), Lyonia lucida (Lam.) K. Koch, and Salix matsudana Koidz. F. tortuosa Rehd. (corkscrew willow). No species produced sufficient flowers, fruits or ornamental stems during this establishment period to allow a florist evaluation of the stems for use as woody floral stems.     

Effect of gap size on mid-rotation stand structure and species composition in a naturally regenerated mixed broadleaf forest

This paper is an assessment of the effect of gap size on stand structure and species composition 48 years following treatment in a mixed broadleaf upland forest. Established in 1960, the study tests three circular openings, 15.2 m (0.02 ha), 45.7 m (0.16 ha), and 76.2 m (0.46 ha). Forty-eight years following treatment (2008) basal area, top height, and quadratic mean diameter were significantly lower in 15.2 m openings. Maple (Acer spp.) species had the highest mean importance value across treatments (0.40). Trends suggest that species composition of dominant and codominant trees among opening sizes may have been influenced by shade tolerance adaptations of the species groups present. Whereas 15.2 m openings were dominated by shade tolerant maple species, 45.7 and 76.2 m openings produced a mixture of commercial species including shade intolerant species such as yellow-poplar (Liriodendron tulipifera L.), trees of intermediate shade tolerance like oak (Quercus spp.), and shade tolerant maple. Data further suggest the density of overstory oak was highest in the intermediate opening size (45.7 m), while yellow-poplar increased in the larger opening sizes. Evaluation of species shifts between 1981 and 2008 showed that relative basal area of maple increased across all treatments. Relative basal areas from 45.7 to 76.2 m openings suggest declines in yellow-poplar and other non-commercial species were balanced by increases in oak and maple.     

Interaction of root-knot nematode and mycorrhizal fungi on common beanPhaseolus vulgaris L.

The interactions of root-knot nematode and VAM fungus on common bean plants (Phaseolus vulgaris L.), and the sequence of nematode infection were studied in the greenhouse. The inoculation with VAM fungus caused a significant increase in plant height and fresh weight compared with non treated plants.Meloidogyne infection unsignificantly decreased plant height and dry weight. When fungus was inoculated at 15 and 30 days prior toM. incognita infection, a significant increase in fresh weight was observed. There were no significant differences in total nitrogen (mg/plant) between plants inoculated withM. incognita alone or those inoculated with bothM. incognita and VAM fungus at the same time or 15 days after the fungus inoculation. Plants preinoculated with VAM fungus 30 days prior to nematode infection had a significant increase in total nitrogen. The inoculation with VAM fungus caused a significant increase in phosphorus content. However, it was significantly decreased in plants inoculated with nematode alone and in plants inoculated with VAM fungus andM. incognita at the same time. Gall index and final nematode population were significantly increased when nematodes were treated at the same time with fungus, although there were significant decrease in nematode final population and gall index when the plants were treated with nematodes at 15 and 30 days after mycorrhizal infection. A decrease in percentage of fungal colonization was observed when nematodes were inoculated with fungus at the same time.     

Shifting contestation into cooperation: Strategy to incorporate different interest of actors in medicinal plants in Meru Betiri National Park,Indonesia

Meru Betiri National Park (MBNP) is home to a variety of medicinal plants that local communities collect for individual use and sale. In MBNP, a variety of actors are interested in medicinal plants for different reasons. This paper analyzes the interest and influence of ten important actors related to medicinal plant collection and use in MBNP: national park management, the Plantation and Forestry Office of Jember District, farmer groups (jaket resi), medicinal plant collectors (pendarung), medicinal plants purchasers (pengepul), small-scale medicinal plant industries of the Toga Sumber Waras, Bandealit plantation company, a conservation NGO (LSM KAIL), loggers (blandong), and log buyers (borek kayu). To examine and map the position of different interests and influences of actors involved in medicinal plant usage, this paper uses a power grid matrix. The analysis confirms that five of the ten aforementioned actors play a direct role in the medicinal plant policy process, while five actors do not and can be categorized as context setters, subjects, or crowd. This paper ends by recommending a strategy for considering policy options that promote shared interests and minimize anticipated objection from actors concerning the harvest of medicinal plants in MBNP. It concludes that the utilization of medicinal plants in MBNP, together with protection of natural resources, should become an integral part of the park's conservation strategy.     

Functional traits and plasticity linked to seedlings’ performance under shade and drought in Mediterranean woody species

Interspecific differences in morphology, biomass allocation and phenotypic plasticity along an experimental irradiance gradient and two contrasting water regimes were studied for eight Mediterranean woody species at the seedling stage; a critical demographic stage in Mediterranean plant communities. We tested whether species variation in these traits can explain previously reported interspecific differences in performance under shade and drought. Four irradiance levels (1%, 6%, 20% and 100% of full sunlight) and two water regimes (well watered and water-stressed conditions) in 6% and 100% irradiance levels were established. Quercus species exhibited the largest seeds, the highest total dry mass and also the highest root-shoot ratio, but their leaf mass fraction (LMF) and leaf area ratio (LAR) were low. Pistacia terebinthus, and Arbutus unedo exhibited the opposite traits. From those traits that correlated with seed size only LAR resulted significantly linked to survival in deep shade. None of the traits studied correlated with survival under water-stressed conditions. Overall phenotypic plasticity was negatively correlated with survival in deep shade but no correlation was found with survival under water-stressed conditions. Our results highlight the importance of low LAR and low phenotypic plasticity as potential determinants of enhanced performance under shade during the very early seedling stages of Mediterranean woody species. Low LAR was also positively correlated with seed size and consequently, its relationship with enhanced performance under shade might change at later life stages of the plant when seed reserves are no longer available.     

Cloning of plasma membrane H-ATPase gene in Populus euphratica Oliv.

For this paper, the plasma membrane (PM) H -ATPase gene has been cloned from Populus euphratica Oliv. through a homology based strategy. The isolated 3,210 bp cDNA contains a single 2,862 bp open reading frame (ORF) which encodes a putative H -ATPase protein of 953 amino acid residues, with a significant homology to plasma membrane H -ATPase of Primus persica, Phaseolus vulgaris, Sesbania rostrata and Daucus carota. The predicted protein has a molecular weight of 104,553 Da. The copy number analysis revealed multiple copies of the PM H -ATPase in the P. euphratica genome after digestion of their genomic DNA by the restriction enzymes EcoRI, NdeⅠ, FbaⅠand BglⅡ, and Southern blot.     

Uptake of nutrients in Calluna vulgaris seed plants grown with and without mycorrhiza

A simple method to inoculate seed plants of heather Calluna vulgaris (L.) Hull with its fungal associate was tested in peat soil under greenhouse conditions. This resulted in colonization of all the pots where inoculation was carried out. The average percentage colonization was 27. Colonization was not observed in the non-inoculated pots. This opens the way for experiments designed to create knowledge of the significance of ericaceous mycorrhiza to the members of the family Ericaceae that typically dominates nutrient-poor sites such as heathland, raised bog and tundra in the Northern Hemisphere. In association with the inoculation, experiments were carried out to determine differences between mycorrhizal and non-mycorrhizal seed plants of heather, as regards the concentration of nutrients (NPK) in the shoots. No significant increase of nutrient concentrations in shoots or aboveground biomass due to the presence of mycorrhiza was observed. Phosphorous concentration was 16% lower in the shoots from the plants inoculated with mycorrhiza; this result was the only significant effect that could be ascribed to mycorrhiza. Increased growth rate in the plants with mycorrhiza dilutes the nutrient concentrations in the shoots from these plants. The mean nitrogen content (g N/pot) in shoots of heather was 10% higher in mycorrhizal plants than in non-mycorrhizal plants, whereas the difference in concentration (g N/g dry matter) was only 2% in favor of mycorrhizal plants. This indicates that the presence of mycorrhiza rather increases the growth rate than the nutrient concentration in the shoots. Fertilizer application experiments were carried out on the same plants. When 10 kg N ha⁻¹ was supplied as NH₃–N in aqueous solution, the concentration of N in the shoots was increased by 14%, from 0.75 to 0.86%. Both these concentrations are lower than those observed in nature. The total growth was increased by 32% in the potassium-fertilized (10 kg K ha⁻¹) pots. The percentage colonization was positively correlated to the N:P ratio in the shoot tissue. None of the treatments influenced the percentage colonization significantly.     

Trees improve water storage and reduce soil evaporation in agroforestry systems on bench terraces in SW Uganda

The success of agroforestry in semi-arid areas depends on efficient use of available water and effective strategies to limit tree/crop competition and maximise productivity. On hillsides, planting improved tree fallows on the degraded upper section of bench terraces is a recommended practice to improve soil fertility while cropping continues on the lower terrace to maintain food production. This study examined the influence of tree fallows on soil water content (θ _w ) and evaporation (E _s ). Alnus acuminata Kunth (alnus), Calliandra calothyrsus Meissner (calliandra), Sesbania sesban L. (sesbania), a mixture of all three species, or sole crops (beans (Phaseolus vulgaris L.) or maize (Zea mays L.)) were grown on the upper terrace. The same sole crops were grown on the lower terrace. Four management regimes (unpruned, root, shoot and root + shoot pruned) were applied to the tree rows adjacent to the cropping area. Neutron probe and microlysimeter approaches were used to determine θ _w and E _s when the trees were c. 3.5 years old. Sesbania and alnus increased θ _w by 9–18 % in the cropping area on the lower terrace but calliandra reduced θ _w by 3–15 %. After heavy rain, E _s comprised 29–38 % of precipitation in the tree-based treatments and 53 % under sole crops. Absolute values declined as rainfall decreased, but E _s as a proportion of rainfall increased to 39–45 % in the tree-based treatments and 62 % for sole crops. Root + shoot pruning of alnus and the tree mixture increased θ _w in the cropping area but had no significant effect in the other tree-based treatments. The results suggest that sesbania and alnus can be planted on smallholdings without compromising water supply to adjacent crops, whereas calliandra decreased water availability despite reducing E _s . These results provide a mechanistic understanding of reported effects on crop yield in the same site.     

Alley cropping Sesbania sesban (L) Merill with food crops in the highland region of Rwanda

Food production in the densely populated Rwandan highlands is impeded by soil erosion and loss in fertility. Alley cropping leguminous shrubs with food crops on contours is purported to minimize the problem and to provide wood and forage. This study reports the effect of Sesbania prunings plus moderate levels of N and P on bean (Phaseolus sp) and maize (Zea mays) yields in alley cropping. Experimental design was a randomized complete block with split-split plots. Main plots were alley width: 2, 4, 6 and 8 m. Phosphorus (P) at 0, 30 and 60 kg P₂O₅/ha occupied the subplot and nitrogen (N) at 0, 30 and 60 kg/ha were assigned at the sub-sub plot level. No P was applied to maize during the second cropping season. Crop yield in kg/ha included the land space taken by hedgerows. Bean yield in 6 m alleys (1100 kg/ha) was about twice that in 2 m alleys (500 kg/ha). Bean responded to N and P. Optimum alley width and N for bean yield were 6 m and 30 kg/ha, respectively. Cuttings from alley hedgerows provided stakes for climbing beans. Maize responded to N but not to residual P. The highest maize yield came from 8 m alleys with 40 kg/ha, but yields from 8 and 6 m alleys with the same N treatment were not significantly different. Maize plants in middle rows were significantly taller than plants in rows adjacent to hedgerows. Maize rust development showed significant alley width and row position effect. There were significantly fewer uredinia in the Sebania alleys relative to the control plots without shrub hedgerows. Rust development on maize in middle rows was significantly greater than development in border rows.     

Incidence and Severity of Bean Rust (Uromyces appendiculatus) in Alleys between Leucaena Hedgerows in Kenya

The effects of inter-row spacing of Leucaena leucocephala (Lam.) de Wit in an alley cropping system on the incidence and severity of rust (Uromyces appendiculatus (Pers.) Unger) on intercropped beans (Phaseolus vulgaris L.) and their yield were examined over 2 years (1993 and 1994) at Chepkoilel Campus in Kenya. Each experiment consisted of three randomized blocks with treatments of three alley widths (2 m, 4 m and 8 m) and a treeless control with two intra-row spacings of Leucaena (0.5 m and 1.0 m). Hedgerows were coppiced at 1.0 m height and pruned subsequently at 2–3 months intervals. No fertilizer was applied but Leucaena loppings were incorporated as green leaf manure. Rust on beans was assessed at three growth stages in each season, using the Centro International de Agricultura Tropical (CIAT) scales. Microclimate was monitored in treatments, in 1994. Bean growth and yield were also measured. Rust increased with increasing alley width and was less severe in bean rows adjacent to hedgerows. Bean yield was highest in the treeless control plots and declined with decreasing alley width. Beans in 2 m alleys had significantly lower (p < 0.05) yields than 8 m alleys and treeless control plots. Bean growth was greatly modified in 2 m alleys and close to hedgerows. Light availability and diurnal temperature increased with alley width but relative humidity and leaf wetness duration decreased. Proximity to hedgerows also had marked effect on microclimate. The changes in yield, rust incidence and severity were examined in relation to microclimate, inoculum survival and dispersal.     

Woody understory plant diversity in pure and mixed native tree plantations at La Selva Biological Station,Costa Rica

Tree plantations can be an important tool for restoration of abandoned pasturelands in the tropics. Plantations can help speed up secondary forest succession by improving soil conditions, attracting seed-dispersal agents, and providing shade necessary for understory growth. In this study, abundance and richness of understory regeneration was measured in three native tree plantations 15–16 years of age at La Selva Biological Station in the Costa Rican Caribbean lowlands. Each plantation contained tree species in pure plots, a mixture of the species, and natural regeneration plots (no trees planted). The greatest abundance of regeneration was found in the understory of pure plots of Jacaranda copaia (Aubl.) D.Don., Vochysia guatemalensis Donn.Sm., Dipteryx panamensis Benth, Vochysia ferruginea Mart., and in two mixed stands, while the lowest was found in the natural regeneration treatments with about half the values as in the plantation stands. There was a significant negative correlation between percent canopy openness and abundance of regeneration in the understory. Two distinctive clusters separated the regeneration treatments from the mixed and pure plantations at a very low Bray–Curtis similarity value. The natural regeneration treatments are separated from mixed and pure plantations in the two-dimensional ordination. The lack of difference between the understory make-up of pure and mixed plantations in abundance, species richness, and seed-dispersal syndromes of understory species suggests that planting mixed stands is not necessarily superior to planting pure stands for promoting understory diversity of woody species. While regeneration of woody species can be faster under pure- or mixed-species plantations than in open pastures, the abundance, richness and species composition depends on each plantation species, or species assemblages in case of the mixtures.     

Bewegungsbehinderung von Arthropoden durch Trichome an Bohnenpflanzen (Phaseolus vulgaris L.)

Hindrance of Arthropods by trichomes of bean-plants (Phaseolus vulgaris L.) On the leaves ofPhaseolus vulgaris are hooked, shorter and longer shaped trichomes. On occasion of suitable conditions of arrangement and combination of the trichomes Arthopods become entangled in the aforesaid structures. Above all Aphidid-Imagines, hardly often Aleyrodid-Imagines are caught by these leaves and die prematurely. It is possible to prevent Aphidid-Imagines from parturiation by means of the trichomes so as to reduce their actual fertility on particular beans. But there is hardly no prevention for the larvae of Aphididae and Aleyrodidae as well as for any phase of Tentranychidae. A survey of relevant conditions in the Grazer Feld is given with reference to questions which are still unanswered.     

Effects of shade on growth, biomass allocation and leaf morphology in European yew (Taxus baccata L.)

The impact of shade on the growth of European yew (Taxus baccata L.) saplings was investigated over a three-year period using artificial shading to simulate four different light regimes (3, 7, 27 and 100 % relative photosynthetic photon flux density, RPPFD). There was no mortality attributable to shading even under the 3 % RPPFD treatment. Increasing shade was positively associated with specific leaf area, leaf length, leaf width and total chlorophyll content, but negatively associated with plant height, stem diameter, total dry weight and root to leaf and shoot ratio. Discoloration of the foliage occurred in plants grown in 100 % RPPFD conditions (resulting in reduced growth rates) and those transferred to 100 % RPPFD conditions after being shade-acclimated for 2 years. Evidence suggests that T. baccata has the ability to regenerate beneath a lighter canopy but beneath denser canopies gap dynamics will play an important role in facilitating successful regeneration and this needs to be reflected in management of natural populations of this declining species.