Harvesting fodder trees in montane forests in Kenya: species,techniques used and impacts

There has been an increasing interest in fodder trees and their potential to help the rural poor. However, few studies have addressed the ecological impacts of fodder tree harvesting. We investigated the species harvested and the techniques used, and the effects of fodder harvesting on (1) species’ populations and (2) forest carbon stocks in three montane forests in Kenya. Focus-group discussions were organized in 36 villages to determine which species were harvested and with which techniques. Field observations were made on vegetation plots: stem diameter, tree height, species and extent of harvest were recorded. Carbon stocks were calculated using an allometric equation with (1) observed height of harvested trees, and (2) potential height estimated with a power model, and results were compared. Eight tree species were commonly harvested for fodder using different techniques (some branches, main stem, most branches except stem apex). Fodder harvesting (together with other uses for some species) negatively affected one species populations (Olea europaea), it did not negatively affect four (Drypetes gerrardii, Gymnosporia heterophylla, Pavetta gardeniifolia, Xymalos monospora), and more information is needed for three species (Olea capensis, Prunus africana, Rinorea convallarioides). Fodder harvesting did not significantly reduce forest carbon stocks, suggesting that local communities could continue using these fodder trees if a carbon project is established. Among the fodder species studied, X. monospora could be used in reforestation programs, as it has multiple uses and can withstand severe pruning. Although our study is only a snapshot, it is a baseline which can be used to monitor changes in fodder harvesting and its impacts related to increasing droughts in northern Kenya and increasing human populations.     

Response of bird communities to selection harvesting in a northern tolerant hardwood forest

We investigated the responses of forest birds to habitat changes following timber harvest by selection cutting in three northern tolerant hardwood forest stands using a before–after control-impact (BACI) type of experimental design. We observed only minor effects on the bird community associated with mature forests. Ovenbird (Seiurus aurocapilla) abundances declined by about 80–90% in two of the three harvested blocks. Black-throated blue warblers (Dendroica caerulescens) declined in abundance by about 70% on a single block 2 and 3 years post-harvest. Mechanical disturbance of the shrub layer [primarily Canada yew (Taxus canadensis)] was coincident to this decline. Several bird species that prefer early successional or shrubby habitats, such as veery (Catharus fuscescens), cedar waxwing (Bombycilla cedrorum), chestnut-sided warbler (Dendroica pensylvanica), magnolia warbler (Dendroica magnolia), American redstart (Setophaga ruticilla), mourning warbler (Oporornis philadelphia) and white-throated sparrow (Zonotrichia albicollis), benefited from selection cutting, with the timing of individual species’ responses related to changes in habitat structure and composition. Effects in one block were still evident 7 years after harvest. Guidelines that support a residual stocking target of 20 m²/ha should promote the retention of mature forest bird communities, including ovenbird, while still providing habitat for early successional bird species.     

How rare is too rare to harvest?: Management challenges posed by timber species occurring at low densities in the Brazilian Amazon

Tropical forests are characterized by diverse assemblages of plant and animal species compared to temperate forests. Corollary to this general rule is that most tree species, whether valued for timber or not, occur at low densities (<1 adult tree ha⁻¹) or may be locally rare. In the Brazilian Amazon, many of the most highly valued timber species occur at extremely low densities yet are intensively harvested with little regard for impacts on population structures and dynamics. These include big-leaf mahogany (Swietenia macrophylla), ipê (Tabebuia serratifolia and Tabebuia impetiginosa), jatobá (Hymenaea courbaril), and freijó cinza (Cordia goeldiana). Brazilian forest regulations prohibit harvests of species that meet the legal definition of rare – fewer than three trees per 100 ha – but treat all species populations exceeding this density threshold equally. In this paper we simulate logging impacts on a group of timber species occurring at low densities that are widely distributed across eastern and southern Amazonia, based on field data collected at four research sites since 1997, asking: under current Brazilian forest legislation, what are the prospects for second harvests on 30-year cutting cycles given observed population structures, growth, and mortality rates? Ecologically ‘rare’ species constitute majorities in commercial species assemblages in all but one of the seven large-scale inventories we analyzed from sites spanning the Amazon (range 49–100% of total commercial species). Although densities of only six of 37 study species populations met the Brazilian legal definition of a rare species, timber stocks of five of the six timber species declined substantially at all sites between first and second harvests in simulations based on legally allowable harvest intensities. Reducing species-level harvest intensity by increasing minimum felling diameters or increasing seed tree retention levels improved prospects for second harvests of those populations with a relatively high proportion of submerchantable stems, but did not dramatically improve projections for populations with relatively flat diameter distributions. We argue that restrictions on logging very low-density timber tree populations, such as the current Brazilian standard, provide inadequate minimum protection for vulnerable species. Population declines, even if reduced-impact logging (RIL) is eventually adopted uniformly, can be anticipated for a large pool of high-value timber species unless harvest intensities are adapted to timber species population ecology, and silvicultural treatments are adopted to remedy poor natural stocking in logged stands.     

Post-fire germination: The effect of smoke on seeds of selected species from the central Mediterranean basin

In regions with a Mediterranean-type climate wildfires are a frequent occurrence: in such environments fire tolerant/favoured species are frequently encountered. In the Mediterranean basin, many species of fire prone habitats are resprouters while others are known to germinate after fire. Fire causes an enhancement of seed germination in many species from fire prone habitats in the other regions with a Mediterranean-type vegetation such as Western Australia, California and South Africa. Seeds of a number of these species are stimulated to germinate by the smoke generated from burning of plant material in either an aerosol or aqueous form. However, for species from the Mediterranean basin the role of smoke in germination is poorly known, despite the fact that in the field many species seems to be encouraged to germinate after fire. We examined the germination of 10 species native to the Mediterranean basin that were treated with aerosol smoke. Some species were from fire prone habitats while others were not. In relation to the controls, increased germination occurred in three of the species (e.g. Cistus incanus), three had more rapid germination but no total increase (e.g. Rhamnus alaternus), two showed reduced germination (e.g. Asphodelus ramosus) and two exhibited no difference in germination (e.g. Clematis flammula). There was additionally no consistent pattern of germination behaviour depending on the habitat from which the species came. Comparison is made between the results of this study and those of other studies on seed germination response to heat and smoke in other areas of Mediterranean-type climate. An understanding of the importance of fire in relation to other disturbances in the vegetation dynamics in the Mediterranean basin needs to be clarified by further detailed studies of the effect of heat and smoke products on seed germination of Mediterranean species. Outcomes of further research, also on a broader range of species, would have important impacts also for conservation, environment management, horticulture and ecosystem restoration.     

Thinning and chipping small-diameter ponderosa pine changes understory plant communities on the Colorado Front Range

Novel fire mitigation treatments that chip harvested biomass on site are increasingly prescribed to reduce the density of small-diameter trees, yet the ecological effects of these treatments are unknown. Our objective was to investigate the impacts of mechanical thinning and whole tree chipping on Pinus ponderosa (ponderosa pine) regeneration and understory plant communities to guide applications of these new fuel disposal methods. We sampled in three treatments: (1) unthinned forests (control), (2) thinned forests with harvested biomass removed (thin-only), and (3) thinned forests with harvested biomass chipped and broadcast on site (thin + chip). Plots were located in a ponderosa pine forest of Colorado and vegetation was sampled three to five growing seasons following treatment. Forest litter depth, augmented with chipped biomass, had a negative relationship with cover of understory plant species. In situ chipping often produces a mosaic of chipped patches tens of meters in size, creating a range of woodchip depths including areas lacking woodchip cover within thinned and chipped forest stands. Thin-only and thin + chip treatments had similar overall abundance and species richness of understory plants at the stand scale, but at smaller spatial scales, areas within thin + chip treatments that were free of woodchip cover had an increased abundance of understory vegetation compared to all other areas sampled. Relative cover of non-native plant species was significantly higher in the thin-only treatments compared to control and thin + chip areas. Thin + chip treated forests also had a significantly different understory plant community composition compared to control or thin-only treatments, including an increased richness of rhizomatous plant species. We suggest that thinning followed by either chipping or removing the harvested biomass could alter understory plant species composition in ponderosa pine forests of Colorado. When considering post-treatment responses, managers should be particularly aware of both the depth and the distribution of chipped biomass that is left in forested landscapes.     

Do aggregated harvests with structural retention conserve the cavity web of old upland forest in the boreal plains?

Boreal species that are dependent on old forests, such as many cavity-using birds and mammals, are at high risk from conventional harvest practices. These species may benefit from ecologically sustainable forest management practices that increase heterogeneity within stands and across landscapes. Structural retention within cutblocks and spatial aggregation of cutblocks into large (1000s ha) harvest units are two such management practices being implemented by forestry companies in the boreal plains of Alberta and Saskatchewan. However, little is known about the implications of these practices for old forest species. The goal of our study was to determine if the cavity-using assemblage associated with old upland forest in this region is retained within aggregated harvests with structural retention. We used a cavity web approach to describe and contrast interactions among cavity excavators (woodpeckers, chickadees, and nuthatches) and the secondary (i.e. non-excavating) species reusing their cavities. We described the cavity web for two intact landscapes of old upland forest and for two aggregated harvest landscapes. We identified four key excavators of intact forest: yellow-bellied sapsucker (Sphyrapicus varius), hairy woodpecker (Picoides villosus), northern flicker (Colaptes auratus), and pileated woodpecker (Dryocopus pileatus). These woodpeckers should be considered key excavators primarily of mature and old aspen forest, which dominated the study landscapes. Each woodpecker filled a unique role in the cavity web and all are important for conservation of two mammal and three bird species that used their cavities. In the short term (i.e. within four years post-harvest), the key cavity excavators and many secondary cavity-using species associated with intact forest were retained in the harvested landscapes. One secondary species (American kestrel (Falco sparverius)) was unique in the harvest cavity web. Compared to the intact cavity web, the harvest web had lower abundance of sapsuckers, greater abundance of flickers, and high reuse of flicker cavities by kestrels. These differences were associated with the shift from intact forest to a landscape characterized by patches of old forest surrounded by early-successional habitat. Abundances of hairy and pileated woodpeckers were too low to detect differences between intact and harvested landscapes. The key excavators primarily used trembling aspen (Populus tremuloides) for cavity trees and thus aspen should be targeted for retention in harvested landscapes. A more detailed examination of the habitat requirements of the key excavators is needed to develop best practices for tree and patch retention and ensure conservation of the cavity-using assemblage in aggregated harvests.     

Using the LANDIS model to evaluate forest harvesting and planting strategies under possible warming climates in Northeastern China

The Small Khingan Mountains in northeastern China provide most of the timber and wood products in the country. Evaluating the long-term effects of harvesting and planting strategies is important especially as the climate changes. In this study, we evaluated the effects of the projected climate warming on potential changes in species’ coverage (percent cover), area harvested (percentage of the study area) and species harvested, using the LANDIS model. Our evaluation was based on the harvest and planting plans specified in Natural Forest Protection Project (NFPP). Our simulated results show that the coverage of southern species such as Korean pine (Pinus koraiensis) and ribbed birch (Betula costata) increases, whereas the coverage of northern species like larch (Larix gmelinii), Kingan fir (Abies nephrolepis), spruces (Picea koraiensis and P. jezoensis) and Dahur birch (Betula davurica) decreases under the warming climate in the region. The species harvested primarily consist of the southern species, especially deciduous species under the warming climate. The warming climate leads to 11.2% increase in area harvested compared to that under the current climate, when planting is not simulated. When planting is simulated, tradeoffs between planting and area harvested are complex. The area harvested only increases in places where moderate planting is implemented, and decreases in places with both low (≤5% area planted) and high (≥30%) planting percentage. This is because when the planting percentage is low, the rate of increase of harvestable species due to planting is lower than the rate of decrease of warming-declining species. When the planting percentage is high, the rate of increase of planted species is higher than the rate of colonization of warming-adapted deciduous species, and the planted species delay the establishment of the warming-adaptable species that have short harvest rotations (due to lower harvestable ages). Our results suggest that the management strategy with planting area of 20% is the best among all the scenarios simulated. Under this warming climate, moderate planting area (e.g. 20%) increases the area harvested to about 43%, which is still less than that (58%) designated in the NFPP. These results have important implications for forest managers designing sustainable forest harvest and reforestation strategies for the landscape under the warming climate.     

Influences of postfire salvage logging on forest birds in the Eastern Cascades,Oregon, USA

In coniferous forests of western North American, fire is an important disturbance that influences the structure and composition of floral and faunal communities. The impacts of postfire management, including salvage logging and replanting, on these forests are not well known. We compared densities and relative abundances of forest birds after fire in unsalvaged stands and stands subjected to one of two intensities of salvage logging (moderate, 30 snags retained per ha and heavy, 5–6 snags retained per ha) in mixed-conifer forests in central Oregon. We used analysis of variance with repeated measures to evaluate three hypotheses concerning the influence of different intensities of salvage on densities or relative abundances of sixteen species of birds, and two hypotheses concerning the influence of time since salvage logging on relative abundances or densities of birds. We also examined the relationship between vegetation and abundances of each bird species. We did not detect significant differences among treatments in densities or relative abundances for eight species and one genus of birds. We detected significant differences for seven species, though the patterns differed among species. Relative abundances or densities of the black-backed woodpecker (Picoides arcticus), hairy woodpecker (P. villosus), brown creeper (Certhia americana), western wood-pewee (Contopus sordidulus) and yellow-rumped warbler (Dendroica coronata) were lower in the heavy and moderate salvage treatment compared to the unsalvaged treatment, while densities of the dark-eyed junco (Junco hyemalis) and fox sparrow (Passerella iliaca) were greater in the moderately and heavily salvaged stands than in the unsalvaged treatment. We detected significant differences between years for four species of birds. Our findings suggest that both cavity-nesting and cup-nesting species respond to salvage logging, and that some species respond uniquely to habitat features influenced by salvage logging. For species that responded negatively to salvage logging, the moderate salvage intensity did not appear to mitigate the negative influence of salvage logging. Areas of unlogged burned forest appear to provide important habitat for some species of birds following forest fires. Our findings parallel those of other recent studies of these species, suggesting robust patterns that transcend particular locations.     

Individual growth, reproduction and population dynamics of Dioon merolae (Zamiaceae) under different leaf harvest histories in Central Chiapas, Mexico

Leaves of the long-lived Dioon merolae have been harvested intensively for decades (possibly for centuries) for ceremonial purposes by Zoque and mestizo groups inhabiting the Central Depression of Chiapas, Mexico. Over a period of four years, we evaluated vital rates (stem growth, leaf production, reproductive performance, and survival) and projected population growth rates in three populations (250 plants each, divided into eight size classes: new germinants, seedlings, saplings (S1, S2), and adults, A1-A4) with different leaf harvesting histories: non-defoliated by humans for at least 55 years (or very old harvest), defoliated annually until 15 years ago (recovering from harvest), and defoliated annually for at least the past 25 years (currently being harvested intensely). Population structure was affected by leaf harvest history. Stem growth was negatively affected by the annual harvest of leaves in size classes from seedlings up to A4 (ANOVA, P < 0.003); fewer leaves were produced by seedlings, saplings and adults at the annually harvested site (ANOVA, P < 0.027). Survival was high at all sites across all size classes; in the annually harvested site, A4 plants showed a decrease in survival (one dead out of four plants). Sex ratio of adults that produced cones during the four years of study was 61% males to 39% females. At the non-defoliated site, adult classes A2 and A4 produced >80% of the cones; no cones were produced by the A3 and A4 adult size classes at the annually harvested site. Asymptotic estimates of population growth indicated growing populations (λ ≥ 1); the highest mean values of finite population growth rate were obtained in the non-harvested site (λ = 1.0202). Elasticity analysis with population projection matrices indicated that stasis (L, 9-38%) was the component that most contributed to λ, followed by growth (G, 1.2-2.9%), and fecundity (F, 0.2-1.1%). We observed detrimental effects on several vital rates due to continued long-term defoliation, although population growth parameters do not currently suggest a decreased trend as a result of the annual harvest of leaves. The duration of this study of a very long-lived plant species suggests caution when setting levels and frequency of leaf harvest. The results help pinpoint practical recommendations that could be implemented in a sustainable management plan for this species, particularly to increase seed production in the annually harvested site, and recruitment of new germinants and seedlings at all sites. However, sound practices will need to consider the interests of involved stakeholders (landowners, pilgrims, conservation organizations and authorities) to effectively reduce anthropogenic pressure on this endangered species.     

Species richness and guild composition in rubber plantations compared to secondary forest on Hainan Island, China

Currently, the one of great threats to tropical biodiversity is the conversion of natural ecosystems to agriculture, and this threat is particularly critical on Hainan, the largest tropical island in China and a global biodiversity hotspot. Rubber (Hevea brasiliensis) has been planted on Hainan since the 1950s, resulting in extensive replacement of native forest, and the rate of this transformation has increased with latex prices since the 1990s. Rubber plantations now cover ca. 506,680 ha on Hainan and reach ca 1,000 m in elevation. To investigate the effect of this land-use change, we compared avian communities between a rubber plantation and a native secondary semi-deciduous monsoon forest. We found that species richness was higher in the native forest than in rubber, and that community composition differed greatly between the two habitats. No strict frugivores were recorded in rubber and no granivores in semi-deciduous monsoon forest. In both richness and abundance, more nectarivores and fewer insectivores occurred in rubber than in the native forest. Some common forest species, as well as protected species, were found only in native forest, including Hainan Partridge (Arborophila ardens), Red Junglefowl (Gallus gallus), Emerald Dove (Chalcophaps indica), Black-browed Barbet (Megalaima oorti), Blue-rumped Pitta (Pitta soror), Puff-throated Bulbul (Alophoixus pallidus), and Chestnut Bulbul (Hemixos castanonotus). Although ten babbler species were found in the native forest, only two were in rubber. Among the species missing in rubber was the endemic Hainan species Grey Laughingthrush (Garrulax maesi). Its endangerment through habitat conversion is of particular conservation concern.     

Are gullies best for biodiversity? An empirical examination of Australian wet forest types

A relatively common observation in forest environments has been that gullies support higher species richness and individual abundance than elsewhere in the landscape. We completed a detailed case study of birds to contrast species richness and assemblage composition between gullies and other parts of the topography of landscapes in three closely related and spatially adjacent wet ash forest types – those dominated by Mountain Ash (Eucalyptus regnans), Alpine Ash (E. delegatensis) or Shining Gum (E. nitens) – in the Central Highlands of Victoria, south-eastern Australia. We also quantified the influence of a wide range of other measures of stand structure and plant species composition on the bird assemblage and on individual bird species.     

Effects of spruce beetle infestations on berry productivity on the Kenai Peninsula,Alaska

Understanding the dynamics of berry productivity provides significant insight for managing the landscape to maintain ecosystem functions. On the Kenai Peninsula, as many as 14 mammal and 30 bird species commonly feed on berries produced by shrubs and forbs associated with spruce forests. Brown bears (Ursus arctos) and black bears (Ursus americanus), in particular, rely on berry crops for foraging. Gathering berries for subsistence or recreation purposes is also important to local residents and visitors. Recent spruce beetle (Dendroctonus rufipennis Kirby) infestations on the Kenai Peninsula have altered the dynamics of berry productivity. To assess this relationship, we evaluated the number and productivity of berries with the following environmental covariates: canopy cover, overstory type, infestation level, year of infestation, land type, and land type association. Data were sufficient to describe the relationships of these variables with the productivity of bunchberry dogwood (Cornus canadensis), black crowberry (Empetrum nigrum), false toadflax (Geocaulon lividum), strawberryleaf raspberry (Rubus pedatus), lingonberry (Vaccinium vitis-idaea), and a combination of 24 other species. We accomplished this using log-linear regression by which we estimated the variance using the negative binomial distribution. Canopy cover significantly influenced the productivity of all berry species except for false toadflax. Increasing canopy cover had a negative effect on berry productivity except for strawberryleaf raspberry. Overstory type influenced the productivity of all individual berry species. Infestation level was significantly related to the productivity of black crowberry, false toadflax, and the combined species group. Berry counts were generally lower in plots with low or medium infestation than in plots with high infestation. Relating the dynamics of berry productivity to the effects of spruce beetle infestations provides the opportunity for better management of post-beetle-infested forests.     

Small-mammal responses to pine regeneration treatments in the Ouachita Mountains of Arkansas and Oklahoma,USA

We compared the initial effects of four forest regeneration treatments (single-tree selection, group selection, shelterwood, and clearcut), and unharvested controls (mature, second-growth forest) on relative abundance of small mammals and small-mammal habitat throughout the Ouachita Mountains of western Arkansas and eastern Oklahoma. We compared small-mammal capture rates in 20 forest stands (4 replicates of 5 treatments) for 2 years prior to harvest treatments, and 1.5, 3.5, and 5.5 years after treatment. We also examined relationships among small mammals, treatments, and habitat conditions. Before harvest, all stands where characterized by high basal areas (BA), little understory vegetation, and low small-mammal capture rates. Compared with pre-harvest numbers, the number of individuals captured increased nearly five-fold in treated stands 1.5 years after harvest. After harvest, capture rates for all taxa combined were significantly greater in harvested stands (regardless of treatment) than in unharvested controls. Fulvous harvest mice (Reithrodontomys fulvescens) capture rates were greatest in clearcuts. Fulvous harvest mice, cotton rats (Sigmondon hispidus), and pine voles (Microtus pinetorum) were associated with abundant herbaceous vegetation in the understory and low BA. Eastern woodrats (Neotoma floridana), golden mice (Ochrotomys nuttalli), and Peromyscus spp. were associated with moderate to dense woody vegetation in the understory and intermediate BA levels. No taxon of terrestrial small mammal was captured exclusively in unharvested stands; most taxa we captured appear to be either disturbance-adapted or tolerant to disturbances from timber harvest.     

The effects of three regeneration harvest methods on plant diversity and soil characteristics in the southern Appalachians

We evaluated the effects of three regeneration harvest methods on plant diversity and soil resource availability in mixed-hardwood ecosystems. The study area is in the Wine Spring Creek watershed on the Nantahala National Forest of the Southern Appalachian Mountains in western North Carolina. The regeneration treatments were: an irregular, two-aged shelterwood cut (2A), with 5.0 m²/ha residual basal area; a shelterwood cut (SW), with 9.0 m²/ha residual basal area; a group selection cut (GS), with 0.10–0.20 ha openings and 25% overstory removal on area basis at first entry; fourth, the control, consisted of two uncut sites (UC). Each harvest treatment was replicated three times across the landscape in similar plant community types. Within each treatment area, permanent plots were marked and inventoried for overstory, midstory, and herbaceous layer plants. In each permanent plot, we collected soil samples in winter (December–March) to reduce temporal variation due to vegetation phenological stage and rainfall events. We analyzed soil samples for extractable calcium (Ca), magnesium (Mg), potassium (K), cation exchange capacity (CEC), pH, bulk density, A-horizon depth, total carbon (C), and nitrogen (N). Species diversity of overstory, understory, and herbaceous layer species was evaluated using species richness (S), Shannon–Wiener's index of diversity (H′), and Pielou's evenness index (E). We used direct gradient analysis (non-metric multidimensional scaling, NMS) to explore the changes in vegetation–site relationships among herbaceous layer abundance, and soil characteristics and overstory basal area between pre-harvest (1994) and post-harvest (2000). Twelve minor overstory species were cut from the 2A treatments and nine species were cut from the SW treatments. Thus, it is not surprising that S and H′ were reduced in the overstory on the heavily cut sites. However, most of these species sprouted from cut stumps and were substantially more abundant in the midstory layer after harvest than before. For the midstory, we found higher S and H′ on the harvested treatments than the control; however, H′ did not differ significantly among the harvest treatments. We measured an increase in herbaceous layer H′ on the more heavily cut treatments (2A and SW) after harvest. We found an increase in average distance in the NMS ordination among sites in 2000 compared to 1994, which suggests greater herbaceous species diversity after harvest. However, we did not see a clear separation among harvest treatments in the NMS ordination.     

Short-term effects of group-selection harvesting on breeding birds in a northern hardwood forest

We used a before-after, control-impact design (one year pre-harvest, two years post-harvest) and unlimited-radius point counts to study the effects of typical group-selection harvesting (0.5 gaps ha⁻¹ placed near seed trees within a standard single-tree selection harvest) and intensive group-selection harvesting (4 gaps ha⁻¹ placed on a grid with no harvesting between gaps) on the composition and abundance of breeding birds in tolerant hardwood forests in Algonquin Provincial Park, Ontario. Percent similarity between pre- and post-harvest bird communities was 5–9% lower in selection harvested stands than in reference stands. Differences in percent similarity among the three treatments were not significant, however, suggesting that the changes in the bird community in stands harvested with group selection were not substantially different than those in reference stands. Abundance of aerial foragers and tree-and-shrub nesters increased in response to typical and intensive group selection in the second year post-harvest. By contrast, bark foragers and cavity-nesters decreased in the first year post-harvest and then increased in the second year post-harvest in response to typical group selection. Abundance of 16 (73%) of 22 species was not affected by harvesting. Blue Jay (Cyanocitta cristata), Chestnut-sided Warbler (Dendroica pensylvanica), Least Flycatcher (Empidonax minimus), and White-throated Sparrow (Zonotrichia albicollis) increased in response to intensive group selection in the first or second year post-harvest, whereas Chestnut-sided Warbler, Hairy Woodpecker (Picoides villosus), and White-throated Sparrow increased in response to typical group selection in the first or second year post-harvest. Ovenbird (Seiurus aurocapilla) decreased slightly in response to typical group selection in the second year post-harvest. Our short-term data suggest that intensive, rather than typical, group-selection harvesting is preferred for maintaining densities of cavity-nesting birds and Ovenbird; whether these advantages continue through the remainder of the cutting cycle and beyond requires further investigation.     

Exotic plant species in the southern boreal forest of Saskatchewan

Exotic species possess abilities to harm the ecosystems they invade. This study assesses the density, frequency and cover of exotic plants in roadside right-of-ways, logged areas and wildfire sites within mixedwood sections of the southern boreal forest of Saskatchewan. A total of 23 exotic species were observed including nine species of Gramineae, seven species of Leguminosae and five species of Compositae. Average density of exotic species in areas recently disturbed by timber harvesting or wildfire was 0.2 stems m⁻² with a frequency of 72%. Exotic species adapted for wind dispersal were best represented including common dandelion (Taraxacum officinale), perennial sow thistle (Sonchus arvensis) and annual hawksbeard (Crepis tectorum). Only two exotic species, T. officinale and Canada bluegrass (Poa compressa), were observed in mature forest; both occurred with a frequency of 13% and an average density of 0.002 stems m⁻². A total of 22 exotic species was found in the right-of-ways quadrats with an average density of 117 stems m⁻² and a frequency of 94%. The most frequently observed exotic species in the roadside right-of-way areas were T. officinale, alsike clover (Trifolium hybridum), S. arvensis, creeping red fescue (Festuca rubra) and smooth brome grass (Bromus inermis). These species are either common agricultural weeds or were part of the original seed mixture used to establish a plant cover in the roadside right-of-ways.     

Annual variation in predation and dispersal of Arolla pine (Pinus cembra L.) seeds by Eurasian red squirrels and other seed-eaters

Seed predation and dispersal are key processes in the survival and distribution of plant species. Many animals cache seeds for later consumption, and, failing to recover some of these seeds, act as seed dispersers, influencing post-dispersal seed and seedling survival. Both animal and plant benefit from scatterhoarding and natural selection of seed characteristics and adaptations of seed predators (and dispersers) is one of the most important examples of co-evolution and mutualism. We studied the producer–consumer Arolla pine (Pinus cembra)–red squirrel (Sciurus vulgaris) system in a subalpine forest in the Italian Alps. Arolla pine produced large seed-crops (masting) at irregular intervals, followed by years with poor or moderate seed production. Squirrel density fluctuated in synchrony with the food resource, eliminating the time-lag normally present when resources are produced in pulses. In all years except 2009 (a mast-crop year), all Arolla pine cones were harvested (their seeds consumed and/or cached) by September to late October by different species. Both squirrels and nutcrackers (Nucifraga caryocatactes) fed on seeds, and their relative pre-dispersal predation rates (on cones in the canopy) differed between years. Overall, nutcrackers consumed more seeds between July and October than squirrels, but in 1 year squirrels took the largest number of seeds. Pre-dispersal seed predation by squirrels tended to be lower in years with large seed-crop size and there was a positive correlation, over the entire study period, between density of recovered hoards and Arolla pine seed density of the previous year. We conclude that (i) squirrels and nutcrackers are important pre-dispersal seed predators and seeds dispersers; (ii) squirrels are also post-dispersal seed predators, and (iii) the proportion of cached seeds consumed by squirrels increased with the size of the Arolla pine seed-crop, suggesting that red squirrel is a conditional mutualistic scatterhoarder of Arolla pine seeds.     

广东英德石门台省级自然保护区珍稀植物资源的现状和保护对策

广东英德石门台自然保护区共有珍稀植物45种,国家重点保护植物23种(其中国家I级保护植物2种,国家II级保护植物21种),珍稀濒危植物36种(其中濒危2种,渐危20种,稀有14种)。这些植物具有种类丰富、热带性强、起源古老等特点。在探讨其濒危原因的基础上,笔者提出了一些保护对策,并建议把五岭过路黄等32种植物列为保护植物。     

Population dynamics and management of Amazon tidal floodplain forests: Links to the past, present and future

Although tidal floodplain forests represent the oldest commercial logging frontier in the Amazon, tree demography analyses are lacking. Consequently, the accurate evaluation of impacts of past use and the development of ecologically sound forest management has lagged. To address that gap, we combine matrix model methods with data from interviews with tidal floodplain smallholders regarding land use and ecological knowledge. Here we examine the population dynamics of 8 common tidal floodplain species and explore the link between species population ecology and past, present, and future timber use.Despite the generally high timber stocks due to the dominance of Mora paraensis, these tidal floodplain forests offer challenges to management similar to those seen in tropical forests elsewhere, including low recruitment and species-specific tree growth rates, population densities and size distributions. Furthermore, species population ecology and survey results indicate that the long legacy of forest use in the tidal floodplain forests will influence the future of forest use and management, negatively impacting some species (e.g., Virola surinamensis) while likely benefiting others (e.g., M. paraensis). The observed diameter distributions of species least harvested in the past (e.g., M. paraensis, Licania heteromorpha) follow those derived from stable stage distributions. For other historically harvested species (e.g., Carapa guianensis, V. surinamensis), a larger number of harvest-sized trees for most species would be expected under unlogged conditions, a result corroborated by survey results indicating that maximum log size of long-used timber species has decreased over the past decades.While timber extraction in the Amazon Estuary has endured for centuries, our results suggest long-term timber use does not necessarily entail sustainability; a long history of timber harvesting can also indicate a gradual process of resource depletion as preferred species are sequentially exhausted. If current practices are left unchanged, the prospects for long-term management are likely to decrease further as the densities of preferred high-value species (C. guianensis, V. surinamensis, P. filipes) fall to levels that make management economically unattractive.     

Influence of nonhost plant diversity and natural enemies on the potato leafhopper, Empoasca fabae, and pea aphid, Acyrthosiphon pisum, in alfalfa

We examined the effects of nonhost plant diversity and predators on the potato leafhopper, Empoasca fabae (Harris), the pea aphid, Acyrthosiphon pisum (Harris), and their primary host plant, alfalfa, Medicago sativa L. Potato leafhopper intensity (i.e., leafhoppers/alfalfa stem density) and plant damage (i.e., hopperburn) were significantly greater in alfalfa mono- than in polycultures of alfalfa mixed with nonhost plant species. There was no significant effect of nonhost plant diversity on pea aphid intensity or on predator abundance. Predator:prey ratios were higher in poly- than in monoculture. One predator, Nabis sp., was selected for further study. A microcosm experiment indicated that Nabis is an effective predator of both herbivores, and suggested that nonhost plant diversity may enhance the predation of leafhoppers by Nabis. These results suggest that nonhost plant diversity and Nabis limit leafhopper populations and protect alfalfa from herbivory. The potential for nonhost plants to increase herbivore movement and vulnerability to predation is discussed.