Responses of kukupa (

The kukupa or New Zealand pigeon (Hemiphaga novaeseelandiae) is gradually declining on the New Zealand mainland, due mostly to predation by introduced pest mammals including ship rats (Rattus rattus) and brushtail possums (Trichosurus vulpecula). We report on a co-operative project between Maori landowners, the Department of Conservation, and Manaaki Whenua–Landcare Research researchers to restore a Northland kukupa population and to examine kukupa nesting success in relation to pest abundance. Ship rats and possums were targeted by trapping and poisoning throughout Motatau Forest (350 ha) from 1997 to 1999; only possums were targeted in 2000. All 13 kukupa nests located before pest control started in late 1997 failed at the egg stage, but all seven nests located in 1998–99 successfully fledged young when trapping and tracking indices of possums and ship rats were less than 4%. After pest control, counts of kukupa and some other bird species increased at Motatau compared with counts in a nearby non-treatment block, suggesting numbers of adult kukupa can be increased in small forest areas by intensive pest control. This increase is due at least partly to increased nest success. Evidence from time-lapse video cameras, sign remaining at nests, and nest success rates under different pest control regimes suggest both ship rats and possums are important predators at kukupa nests.     

The potential of small exclosures in assisting regeneration of coffee shade trees in South‐Western Ethiopian coffee forests

Ethiopian Afromontane moist forests where coffee grows as understorey shrub are traditionally managed by the local communities for coffee production through thinning of the shade tree canopy and slashing of competing undergrowth. This management practice has a negative impact on the coffee shrubs, because the removal of shade tree saplings and seedlings reduces the succession potential of the shade tree canopy, which threatens the very existence of the shade coffee production system. We assessed the functionality of small exclosures to initiate coffee shade tree canopy restoration through natural regeneration. Our results show that small exclosures have a strong restoration potential for the coffee shade trees preferred by farmers (Albizia schimperiana, A. gummifera and Millettia ferruginea), as evidenced from their seedling abundance, survival and growth. The regeneration of late‐successional tree species of the moist Afromontane forest was not successful in the small exclosures, most probably due to the low abundance or absence of adult trees as seed sources for regeneration. Therefore, temporary establishment of small exclosures in degraded coffee forest fragments where shade trees are getting old or dying is recommended for sustainable shade coffee production.     

An experimental study of the impacts of understorey forest vegetation and herbivory by red deer and rodents on seedling establishment and species composition in Waitutu Forest, New Zealand

Introduced mammalian herbivores are changing the structure and composition of New Zealand’s forest ecosystems and may modify forest succession after natural disturbances. We studied how introduced ungulates (red deer and feral pigs) and rodents (rats and house mice) affected the rate of recovery (i.e. the engineering resilience) of the forest understorey following artificial disturbance. We imposed disturbances by clearing understorey vegetation dominated by Blechnum ferns in forests on relatively fertile alluvium and elevated infertile marine terraces, and recorded recovery of vegetation (seedling establishment, species composition, cover and volume) in herbivore exclosures and controls. Seedlings quickly established on cleared plots: after 2 years, numbers of woody seedlings and ground cover of vascular plants relative to initial values were similar on cleared and uncleared treatments. Volume of plant biomass <2 m remained low on cleared subplots. Ungulates significantly reduced the re-establishment of woody seedlings ≥ 10 cm tall: only one seedling reached this height outside exclosures, compared with 29 seedlings inside. The number of seedlings <10 cm tall, expressed relative to numbers present pre-clearing, was not significantly affected by ungulates. The species composition of regenerating vegetation was more similar (Jaccard index) to pre-clearing understorey vegetation inside ungulate exclosures than outside. No consistent effect of rodents (primarily house mice) on seedling establishment or species composition was detected after 2 years, and rodent exclosures did not significantly affect survival of seedlings (Griselinia littoralis and Aristotelia serrata) planted as an index of rodent herbivory pressure. No significant differences in vegetation recovery were apparent between forest types. Rapid seedling recruitment in the absence of understorey vegetation and the presence of herbivores provided evidence that understorey vegetation competes with seedlings for light. Ungulate effects were consistent with other experiments that showed herbivores reduced the rate and altered the trajectory of vegetation regrowth after disturbance.     

Light environments occupied by conifer and angiosperm seedlings in a New Zealand podocarp?broadleaved forest

Interaction between conifers and angiosperms in New Zealand?s podocarp?broadleaved forests is a topic of enduring interest. We aimed to determine if the often discontinuous regeneration of the podocarps Dacrydium cupressinum and Prumnopitys ferruginea can be attributed to their seedlings? tolerating less shade than those of angiosperm canopy trees and/or to occupying a narrower range of light environments. We quantified the light environments (% diffuse light availability) naturally occupied by large seedlings (50?200 cm tall) of these two conifers and five co-occurring angiosperms, in an old-growth podocarp?broadleaved forest in the central North Island of New Zealand. Randomisation was used to compare the mean and variance of the light environments occupied by each species with those of the distribution of light environments in the forest understorey. The 10th percentiles of distributions were also calculated as an indicator of the deepest shade tolerated by each species. These parameters showed D. cupressinum to be essentially randomly distributed in relation to light availability, like the angiosperm Beilschmiedia tawa. Although this was also true of the mean light environment of the other conifer, P.?ferruginea, there was marginally significant evidence that this species was underrepresented at the shadiest microsites. In contrast, the angiosperms Elaeocarpus dentatus and Weinmannia racemosa showed strongly non-random patterns, occupying significantly brighter minimum and mean light environments than would be expected by chance. It therefore seems unlikely that the discontinuous population structures of podocarps in many forests result from an intolerance of shade at the large seedling stage. Furthermore, the similarity of the ranges of light environments occupied by D.?cupressinum and P.?ferruginea suggests that reported differences in population structure and successional position of these species are not attributable to differences in seedling shade tolerance.     

Effects of Small Rodent and Large Mammal Exclusion on Seedling Recruitment in Costa Rica1

We examined whether the experimental exclusion of large mammalian and small rodent seed predators had differing effects on seedling recruitment under natural seed rain conditions. In both primary and late‐successional secondary forested areas, exclosure experiments using natural seed densities were designed to assess seedling recruitment. To assess the differences in seedling recruitment, we monitored three exclosure treatments (1.2 m radius/1.5 m height) in two forest types (primary vs. late‐successional secondary forest): (1) fenced exclosures that excluded large mammals; (2) fenced exclosures that excluded both large and small mammals; and (3) open controls. Within each exclosure treatment, we marked and identified all seedlings at the beginning of the experiment (February 2001), followed the marked seedlings' fate for a year, and then marked and identified all new seedlings after a year. Two preliminary findings were generated from these data: for some tree species, small rodents and large mammals have differential effects on seedling recruitment, and the effect of excluding mammals did not differ with habitat type (primary vs. late‐successional secondary forest). These preliminary results highlight the need to examine further how the effects of small rodent and large mammal exclusion may affect species‐specific seed predation and seedling recruitment in a variety of habitat/land use types (e.g., primary forest, late‐successional forest, and early‐successional forest).     

Secondary forest succession differs through naturalised gorse and native kānuka near Wellington and Nelson

The dominant native woody species forming early-successional vegetation on formerly forested sites in lowland New Zealand were kānuka (Kunzea ericoides) and mānuka (Leptospermum scoparium) (Myrtaceae). These have been replaced extensively by gorse (Ulex europaeus, Fabaceae), a naturalised species in New Zealand. Because gorse typically gives way to native broadleaved (angiosperm) forest in about 30 years, it is often considered desirable for facilitating native forest restoration. We tested three hypotheses, derived from the New Zealand literature, on gorse and kānuka: (1) kānuka stands have a different species composition and greater species richness than gorse stands at comparable successional stages; (2) differences between gorse and kānuka stands do not lessen over time; and (3) several native plant taxa are absent from or less common in gorse than in kānuka stands. We sampled 48 scrub or low-forest sites in two regions, Wellington and Nelson. Sites were classified into one of four predefined categories – young gorse, young kānuka, old gorse, old kānuka – based on canopy height of the succession and the dominant early-successional woody species. Few characteristics of the sites and surrounding landscapes differed significantly among site categories, and none consistently across regions. The vegetation composition of gorse and kānuka and their immediate successors differed in both regions, mainly in native woody species. Species richness was often lower in gorse and there were fewer smallleaved shrubs and orchids in gorse. Persistent differences at the older sites suggest the successional trajectories will not converge in the immediate future; gorse leads to different forest from that developed through kānuka. Gorse-dominated succession is therefore not a direct substitute for native successions. We suggest areas of early native succession should be preserved, and initiated in landscapes where successions are dominated by gorse or other naturalised shrubs.     

Interactive effects of introduced herbivores and post‐flowering die‐off of bamboos in Patagonian Nothofagus forests

Question: In November 2000, Chusquea culeou, a bamboo species dominating Andean forest understories in southern Argentina and Chile, massively flowered and died over a north‐south distance of ca. 120 km. Because bamboo is the major forage for large herbivores in these forests, we examined the interactive influences of the bamboo die‐off and herbivory by introduced cattle on understory and tree regeneration. Location: Lanín National Park, Argentina. Methods: Permanent plots, in and outside livestock exclosures, were installed in a Nothofagus dombeyi forest in patches of flowered and non‐flowered C. culeou. Plots were monitored over four years for changes in understory composition and tree seedling densities and heights. Results: After the C. culeou die‐off, new establishment of N. dombeyi was low, both with and without herbivory. Livestock alone directly increased N. dombeyi seedling mortality through physical damage. However, tree seedling browse ratings and height growth were interactively affected by bamboo flowering and herbivory; unfenced plots in flowered bamboo patches had the shortest seedlings, highest browse ratings, and lowest tree seedling annual growth rates. Understory cover was higher where livestock were excluded, and this effect was intensified in the patches of flowered bamboo. Neither herbivory nor bamboo flowering resulted in major changes in species composition, with the exception of Alstroemeria aurea. Conclusion: Effects of livestock on N. dombeyi regeneration were contingent on flowering of C. culeou. Prior to introduction of livestock, N. dombeyi regeneration was probably successful beneath canopy gaps during windows of opportunity following bamboo die‐off, but now livestock impede tree regeneration. Herbivory during bamboo withering periods also produces more open understories, particularly affecting palatable heliophyllous herb species such as Alstroemeria aurea. The results underscore the importance of assessing herbivore impacts on tree regeneration during relatively short periods of potential tree regeneration immediately following rare bamboo flowering and die‐off.     

Regeneration of a Coastal Pine (Pinus thunbergii Parl.) Forest 11 Years after Thinning,Niigata, Japan

To examine the effects of thinning intensity on wind vulnerability and regeneration in a coastal pine (Pinus thunbergii) forest, thinning with intensities of 20%, 30% and 50% was conducted in December 1997; there was an unthinned treatment as the control (total 8 stands). We re-measured the permanent sites to assess the regeneration characteristics 11 years after thinning. In the 50% thinned stand, seedlings aged from 2 to 10 years exhibited the highest pine seedling density and growth. The age composition ranged from 1–3 years with densities of 9.9 and 5.1 seedlings m⁻² in 30% and 20% thinned stands; only 1-year-old seedlings with a density of 6.1 seedlings m⁻² in the unthinned stand. Similar trends were found for the regeneration of broadleaved species such as Robinia pseudoacacia and Prunus serrulata. We speculate that the canopy openness and moss coverage contributed to the regeneration success in the 50% thinned stand, while the higher litter depth and lack of soil moisture induced the regeneration failure in the unthinned stand. The stands thinned at 20% or 30% were less favourable for pine regeneration than the stands thinned at 50%. Therefore, thinning with less than 30% canopy openness (20% and 30% thinned stands) should be avoided, and thinning at higher than 30% canopy openness (50% thinned stand, approximately 1500 stems ha⁻¹ at ages 40–50 years) is suggested for increasing regeneration in the coastal pine forest. The implications of thinning-based silviculture in the coastal pine forest management are also discussed. The ongoing development of the broadleaved seedlings calls for further observations.     

The response of forest floor vegetation and tree regeneration to deer exclusion and disturbance in a riparian deciduous forest,central Japan

The response of forest floor vegetation and regeneration of major treespecies to deer exclusion in a riparian forest were studied for 3 years withtheinteractive effects of natural disturbances. At the start of this study, deerdensity had quickly increased to a fairly high level (29–31 individualskm^–2) during the last decade and had severely reduced theamount of forest floor vegetation in the study area. Dwarf bamboos, which weredominant before, had almost diminished from the forest floor. During the studyperiod, aboveground biomass increased steadily but species diversity did notchange much in the exclosures. Outside the exclosures, the seedlings of alltreespecies were damaged greatly by deer browsing, especially the taller ones. Deerbrowsing had little effect on the emergence of tree seedlings, but deertrampling might have accelerated emergence indirectly by disturbing the soilsurface for some species. Differences in plant responses were also observed fordeer browsing and the presence of dwarf bamboo that strongly inhibits therecruitment of tree seedlings. The nine major species were classified intothreegroups according to the response of seedlings to deer browsing and disturbance.Group 1 consists of the species whose seedling survival is affected bybrowsing,but seldom by disturbances (Phellodendron amurense,Kalopanax pictus, Quercus crispulaandMalus toringo). Groups 2 and 3 consist of species adaptedto tree-fall disturbance (Betula spp.) and ripariandisturbance (Alnus hirsuta var.sibirica, Ulmus davidiana var.japonica, Populus maximowiczii andSalix sachalinensis), respectively, and seedling survivalof these two groups is principally affected by light conditions. The effect ofdeer browsing on seedling survival and growth was greater for Group 2 than forGroup 3.     

Experimenting with methods to control

Tradescantia fluminensis, commonly referred to as ‘tradescantia’, is an invasive weed of canopydepleted forest remnants. Previous research suggests that a reduction of tradescantia biomass to ~80 gm-2 (~40% cover) is compatible with native forest regeneration. I assessed herbicide application, hand weeding and artificial shading as methods for the control of tradescantia in two lowland podocarp/broad-leaved forest remnants in the lower North Island of New Zealand. Herbicide spray and hand weeding, applied to separate experimental plots, did not prevent re-growth of tradescantia after three successive treatments. Re-growth of tradescantia and invasion of other weeds were positively related to light availability, which increased in the more canopy-depleted areas, and negatively related to native forest regeneration measured two years after initial treatment. Artificial shading was the most effective method of control. The biomass of tradescantia was significantly reduced in artificially-shaded plots (2–5% full light; 81.3 ± 10.6 gm-2) relative to non-shaded plots (15–27% full light; 597.6 ± 6.6 gm-2; t4 = 17.38, P< 0.001) after 17 months. Native sub-canopy species were planted into tradescantia to achieve natural shading over large areas of forest. After 2.5 years, 61% of the saplings planted had emerged from the surrounding tradescantia.     

Regeneration of Salix arbuscula and Salix lapponum within a Large Mammal Exclosure: The Impacts of Microsite and Herbivory

Over‐grazing or browsing by large herbivores may result in the loss of individual plant species or entire plant communities. Restoration schemes often involve exclusion of large mammals, but the resulting changes in vegetation may alter other important ecological processes such as regeneration, via changes in microsite availability for seed germination or increases in populations of seedling predators. Working within a large fenced area from which large mammals were excluded, we experimentally tested the effects of microsite, small herbivores, and their interactions on post‐dispersal seed and early seedling mortality of one nationally scarce (Salix arbuscula) and one nationally rare (S. lapponum) species of montane willow. Seeds were sown in three different microsites: natural vegetation, mown vegetation (mimicking grazed sward), and bare ground. Small exclosures and slug pellets were used to examine the effects of small mammal and slug predation, respectively. Survival of seedlings was monitored during the summer following planting. The presence of bare ground, rather than the absence of herbivores, was of over‐riding importance for early seedling survival and establishment. Protecting seedlings from small mammals made no difference to the levels of survival; however, protecting seedlings from slugs (Arion spp.) resulted in approximately 45% of seedlings surviving until the end of the summer compared to only 30% when seedlings were available to slugs. Although excluding large herbivores may increase seed production of existing individuals, the impacts of changes to plant communities on processes such as regeneration need to be considered if restoration projects are to be fully successful.     

Testing associational resistance against pine weevils mediated by Lasius ants attending conifer seedlings

Natural enemies attracted to plants may provide those plants with protection against herbivores but may also protect neighbouring plants, that is through associational resistance. Ant attendance may be an important mechanism for the occurrence of such effects because ants can reduce the damage caused by a wide variety of herbivorous insects. Ants have been shown, in a previous field experiment, to decrease the damage caused by the pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae), a pest species that causes high seedling mortality in forest regeneration areas. In this study, we specifically tested whether seedlings planted close to ant‐attended seedlings experience associational resistance. We did this under laboratory conditions using the ant species Lasius niger (L.) (Hymenoptera: Formicidae). The feeding damage by pine weevils was significantly reduced on seedlings attended by ants. The neighbouring seedlings, however, did not experience associational resistance. Nevertheless, some associational effects were observed as the number of weevils recorded on both ant‐attended and neighbouring seedlings was significantly lower compared with ant‐excluded seedlings.     

Effects of invasive rats and burrowing seabirds on seeds and seedlings on New Zealand islands

Rats (Rattus rattus, Rattus norvegicus, Rattus exulans) are important invaders on islands. They alter vegetation indirectly by preying on burrowing seabirds. These seabirds affect vegetation through nutrient inputs from sea to land and physical disturbance through trampling and burrowing. Rats also directly affect vegetation though consumption of seeds and seedlings. Seedling communities on northern New Zealand islands differ in composition and densities among islands which have never been invaded by rats, are currently invaded by rats, or from which rats have been eradicated. We conducted experimental investigations to determine the mechanisms driving these patterns. When the physical disturbance of seabirds was removed, in soils collected from islands and inside exclosures, seedling densities increased with seabird burrow density. For example, seedling densities inside exclosures were 10 times greater than those outside. Thus the negative effects of seabirds on seedlings, by trampling and uprooting, overwhelm the potentially beneficial effects of high levels of seed germination, seedling emergence, and possibly seed production, which result from seed burial and nutrient additions. Potential seedling density was reduced on an island where rats were present, germination of seeds from soils of this island was approximately half that found on other islands, but on this island seedling density inside exclosures was 7 times the density outside. Although the total negative effects of seabirds and rats on seedling densities are similar (reduced seedling density), the differences in mechanisms and life stages affected result in very different filters on the plant community.     

Proximity is not a proxy for parentage in an animal-dispersed Neotropical canopy palm

We used parentage analysis to estimate seedling recruitment distances and genetic composition of seedling patches centred around reproductive trees of the animal-dispersed Neotropical canopy palm Iriartea deltoidea in two 0.5 ha plots within second-growth forest and one 0.5 ha plot in adjacent old-growth forest at La Selva Biological Field Station in north-eastern Costa Rica. Seedlings were significantly spatially aggregated in all plots, but this pattern was not due to dispersal limitation. More than 70 per cent of seedlings were dispersed at least 50 m from parent trees. Few seedlings were offspring of the closest reproductive trees. Seedling patches observed beneath reproductive trees originate from dozens of parental trees. Observed patterns of seedling distribution and spatial genetic structure are largely determined by the behaviour of vertebrate seed dispersers rather than by spatial proximity to parental trees.     

Direct and indirect effects of understorey bamboo shape tree regeneration niches in a mixed temperate forest

Plant cover plays a major role in shaping the nature of recruitment microsites through direct (resource mediated) and indirect (consumer mediated) interactions. Understorey plants may differentially affect seedling establishment, thus contributing to regeneration-niche separation among canopy tree species. We examined patterns of early tree seedling survival resulting from interactive effects of understorey bamboo (Chusquea culeou) and resident consumers in a mixed temperate Patagonian forest, Argentina. Newly germinated seedlings of Nothofagus dombeyi and Austrocedrus chilensis were planted in bamboo thickets and non-bamboo patches, with or without small-vertebrate exclosures. We found species-specific patterns of seedling survival in relation to bamboo cover. Nothofagus survival was generally low but increased under bamboo, irrespective of cage treatment. Desiccation stress accounted for most Nothofagus mortality in open, non-bamboo areas. In contrast, Austrocedrus survival was highest in non-bamboo microsites, as most seedlings beneath bamboo were killed by small vertebrates through direct consumption or non-trophic physical damage. There was little evidence for a negative impact of bamboo on tree seedling survival attributable to resource competition. The balance of simultaneous positive and negative interactions implied that bamboo presence facilitated Nothofagus early establishment but inhibited Austrocedrus recruitment via apparent competition. These results illustrate the potential for dominant understorey plants to promote microsite segregation during early stages of recruitment between tree seedlings having different susceptibilities to water stress and herbivory. We recognise, however, that patterns of bamboo–seedling interactions may be conditional on moisture levels and consumer activity during establishment. Hence, both biotic and abiotic heterogeneity in understorey environments should be incorporated into conceptual models of regeneration dynamics and tree coexistence in forest communities.     

Tree shelters facilitate brown oak seedling survival and establishment in a grazing‐dominant forest of Bhutan,Eastern Himalaya

Brown oak (Quercus semecarpifolia) forest is essential for ecological and socioeconomic functions, mainly grazing in the Himalayas. The tree has failed to regenerate naturally and is a threatened species. Restoration of brown oaks is crucial to ensure sustainability while maintaining livestock grazing in these habitats. Achieving this requires cost‐effective restoration techniques that are practicable and sympathetic to the multiple uses of the forest. We assessed the combined effect of grazing (control) and three tree shelters (Protex tubes, mesh wires, and wooden frames) on the field performance of oak seedlings in a forest with heavy grazing pressure. Seedling survival and morphological indicators, including seedling height, collar diameter, sturdiness quotient (SQ), and leaf mass per area (LMA) indices, were measured. More than 90% of control seedlings without protective shelters suffered severe browsing and demonstrated significantly lower survival rates compared to tree shelter seedlings, indicating that grazing was the primary factor governing regeneration success. Seedling survival in tree shelters was three times higher, while the height increase was two times higher than the control. Additionally, locally made mesh wire and wooden tree shelters were more effective than Protex and control in producing quality seedlings reflected by the SQ and LMA values. We suggest that tree shelter is a promising option to restore brown oaks due to its efficacy to defend grazing and support the local community's rights to forest grazing. Our finding is expected to support Bhutan's forest policy of incorporating grazing and tree regeneration into forest management.     

The physiological advantage of an ecological filter species, <Emphasis Type="Italic">Indocalamus longiauritus</Emphasis>, over co-occurring <Emphasis Type="Italic">Fagus lucida</Emphasis> and <Emphasis Type="Italic">Castanopsis lamontii</Emphasis> seedlings

Indocalamus longiauritus (a dwarf bamboo) dominates forest understory and functions as an ecological filter to hinder the regeneration of canopy tree species in many temperate forests. However, the physiological mechanism underlying the function of ecological filters is not clear. In this study, we measured leaf-level carbon capture ability and use efficiency of the dwarf bamboo and the co-existing Fagus lucida (beech) and Castanopsis lamontii (chinkapin) seedlings in forest understory and small gaps in a beech–chinkapin mixed forest in the summer of 2005. The results indicated that I. longiauritus exhibited greater carbon capture ability, as indexed by light-saturated photosynthetic rate (P _max), maximal carboxylation rate, maximal electron transport rate and carboxylation efficiency, than the co-occurring F. lucida and C. lamontii seedlings in both forest understory and small gaps. Higher carbon capture ability in I. longiauritus was related to its greater partition of absorbed light energy to photochemistry. I. longiauritus had higher photosynthetic nitrogen use efficiency than F. lucida and C. lamontii seedlings in both light environments. However, water use efficiency (WUE) in I. longiauritus was higher than F. lucida but lower than C. lamontii. This intermediate WUE in I. longiauritus was related to its intermediate light-saturated stomatal conductance. In addition, I. longiauritus reduced metabolic cost by increasing the ratio of P _max to respiration rate, leading to increased net carbon balance. On the other hand, F. lucida and C. lamontii seedlings had greater plasticity of carbon capture ability and leaf structural traits, which might facilitate colonization of gaps and realization of natural regeneration in these species.     

Ship rat demography and diet following possum control in a mixed podocarp–hardwood forest

Control of one pest species may permit increases in abundance of other pests, thereby reducing the overall net benefit from pest control. We provide evidence that control of introduced possums (Trichosurus vulpecula) may increase ship rat (Rattus rattus) abundance in some New Zealand native forests. Ship rat abundance in a podocarp–hardwood forest was assessed using simple interference indices over 14 years (1990–2004) that included two aerial possum-poisoning operations (1994, 2000). Ship rat demography and rat and possum diet were measured from June 2001 to June 2003 when the rat population was increasing after the 2000 poisoning. Mean ship rat abundance indices increased nearly fivefold after possum control and remained high for up to 6 years after the 1994 poisoning. Rat fecundity was high (50–100% of adult females breeding), even during winter, and young animals dominated the population (73% in age classes 1–3) in 2001–2002 when rat numbers were increasing. During 2002–2003, rat abundance stabilised, without marked winter or spring reductions, the population aged significantly (only 32% in age classes 1–3), and fecundity declined to low levels (4–27% of adult females breeding). Although seeds and fruit dominated the diet of rats driving population recovery after control (74.0% of total diet by dry weight), rat fecundity was instead closely correlated with the proportional consumption of invertebrates (r = 0.91). Juvenile survival was correlated with proportional seed consumption (r = 0.75), while adult survival was correlated with combined seed and invertebrate consumption (r = 0.83). Adult rats ate more seeds and fewer invertebrates than juvenile rats. Seeds and fruit also dominated possum diet (52.2% of total diet). These results are consistent with the hypothesis that increased rat abundance following possum control is a consequence of greater availability of, or reduced competition for, seeds and fruit.     

浙江天目山孑遗落叶阔叶树种的种群结构及更新策略

通过对浙江天目山国家级自然保护区内6个孑遗落叶阔叶树种进行群落学调查,分析了不同微地形单元上种群结构、更新途径及更新个体的空间关联性,探讨了不同干扰体系下孑遗落叶阔叶树种的更新策略.结果表明:孑遗落叶阔叶树种具有较强的萌枝能力,种群结构以间歇型为主,部分种类选择长距离扩散,在适宜生境中间歇型更新,如青钱柳、缺萼枫香等;部分种类因生境限制,在不断的地表冲刷干扰下,选择在母树周围进行间歇型更新,如领春木、香果树.在相对稳定的顶坡和坡地上,青钱柳、缺萼枫香、蓝果树、枫香等树种以种子更新占据一次干扰后形成的林窗生境,并通过其固有的萌枝能力增殖树干,形成径级大小相似的多主干植株,迅速占据优势地位.在不稳定的谷床、谷坡和谷头凹地中,香果树、领春木、枫香等树种因频繁干扰导致种子更新受限、植株损伤并常有个体枯死,通过其极强的萌枝能力补充零星更新的幼苗以及干扰造成的个体损伤.基于生境适应、种群更新和竞争策略,将孑遗落叶阔叶树种大致划分为“林窗修复种”和“生境填充种”两个类型,并提出应加强对其特殊生境的保护.     

Characteristics and behaviour of brushtail possums initially moving into a depopulated area

Brushtail possums are controlled extensively in New Zealand because they are a livestock disease vector and have an impact on native biodiversity. Reinvasion of controlled areas and subsequent population recovery is a significant management problem but little attention has been paid to what influences the settlement of possums in depopulated areas. To address this gap we trapped possums out of an area of about 24?ha in native podocarp–hardwood forest and studied reinvasion and settlement in the central c. 14?ha over 22 months. Most new possums were young males, but adults were also trapped. Many of the new possums caught on the study site post-depopulation did not settle there, most likely because they continued to disperse, but some may have returned to their ranges nearby or were residents with a very low probability of capture. This finding highlights the need for better information about the origins and settlement of possums in depopulated areas to improve management of population recovery and long-term sustained control of possums.