Peter J. Bellingham

Sprouting of trees in Jamaican montane forests after a hurricane

1 Forests in the Blue Mountains of Jamaica were damaged by Hurricane Gilbert which passed over the island on 12 September 1988. 2 In plots between 1300-1900 m, recorded 5-41 months after the hurricane, most stems (61.4% of 4949 living stems) and most species (44 of 47 common species) had sprouts. Comparing species, percent of stems sprouting ranged from 0 to 100%. 3 Broken stems sprouted proportionately more than intact stems; completely defoliated stems sprouted proportionately more than those not completely defoliated; there was no difference between uprooted and upright stems; and stems > 10 cm d.b.h. sprouted more frequently and produced more sprouts per stem, than those 30 sprouting stems, four sprouted more from below 2.5 m, five more from above 2.5 m and five had sprouts evenly distributed. For all species combined, approximately equal numbers of stems fell into each of these three categories. 6 Survivorship up to 41 months after the hurricane was higher in stems with sprouts than those without. 7 There was no simple relationship between the frequency of sprouting of species and microenvironments where seed germination and seedling establishment have been recorded. However, eight common species which have rarely been observed to germinate or establish (in a wide range of conditions) had high frequencies of sprouting. We propose that sprouting is an important mechanism by which many species maintain their presence in these forests.

Damage and responsiveness of Jamaican montane tree species after disturbance by a hurricane

A severe hurricane affected Jamaican montane rain forests in 1988. We made local and widespread measurements of tree condition in three periods: prehurricane 1974- 1984 (preh.); hurricane 1984-1989 (h.); and post-hurricane 1989-1992 (post-h.). In the h. period, 7.22% of stems and 4.72% of the total basal area died; crown loss was the most frequent cause of mortality. Among individual tree species, the hurricane caused a large range in mortality (0-26%) and non-fatal damage. Post-h. mortality was greater than mor- tality in the h. period, and varied among species. Post-h. stem growth rates (all species combined) were more than double the prehurricane rates, but species showed a considerable range from no significant increase to eight times greater. We classified 20 common tree species using damage scores (normalized h. mortality, plus normalized change in mortality from preh. to post-h., plus normalized complete crown loss in h.) and response scores (normalized change, preh. to post-h., in recruitment to the ?3 cm dbh size class, plus normalized change in growth rate from preh. to post-h., plus normalized frequency of sprouts). Species were assigned to one of four groups: resistant (11 species), with low damage and low response; susceptible (5 species), with high damage and low response; resilient (1 species), with high damage and high response; and usurpers (3 species), with low damage and high responsiveness. The grouping of species was broadly related to their regeneration requirements. Most species with seedlings usually found under closed canopy were resistant; three of the four species with seedlings usually found on landslides were also resistant. Species with seedlings most frequently found in gaps included resilient, susceptible, and usurper species, but were not usually resistant. It is likely that the three species classified as usurpers will increase their relative abun- dance in the forest in the next decades and that Cyathea pubescens, which was very susceptible, will decrease in relative abundance of adults. Most of the other species are likely to have small changes in their relative abundances. Thus, at present, hurricanes have few long-term effects on the forests, although a change in the disturbance regime may alter this.

An estimate of the number of tropical tree species

Significance People are fascinated by the amazing diversity of tropical forests and will be surprised to learn that robust estimates of the number of tropical tree species are lacking. We show that there are at least 40,000, but possibly more than 53,000, tree species in the tropics, in contrast to only 124 across temperate Europe. Almost all tropical tree species are restricted to their respective continents, and the Indo-Pacific region appears to be as species-rich as tropical America, with each of these two regions being almost five times as rich in tree species as African tropical forests. Our study shows that most tree species are extremely rare, meaning that they may be under serious risk of extinction at current deforestation rates. The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher’s alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼40,000 and ∼53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼19,000–25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼4,500–6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.

Direct and indirect effects of rats: does rat eradication restore ecosystem functioning of New Zealand seabird islands?

Introduced rats (Rattus spp.) can affect island vegetation structure and ecosystem functioning, both directly and indirectly (through the reduction of seabird populations). The extent to which structure and function of islands where rats have been eradicated will converge on uninvaded islands remains unclear. We compared three groups of islands in New Zealand: islands never invaded by rats, islands with rats, and islands on which rats have been controlled. Differences between island groups in soil and leaf chemistry and leaf production were largely explained by burrow densities. Community structure of woody seedlings differed by rat history and burrow density. Plots on islands with high seabird densities had the most non-native plant species. Since most impacts of rats were mediated through seabird density, the removal of rats without seabird recolonization is unlikely to result in a reversal of these processes. Even if seabirds return, a novel plant community may emerge.

Hurricane disturbance accelerates invasion by the alien tree Pittosporum undulatum in Jamaican montane rain forests

Abstract Questions: Do past disturbance, soil nutrients, or species diversity predict the invasion success of the alien tree Pittosporum undulatum in an island montane rain forest? What are the consequences of its invasion for forest composition and species diversity? Location: Blue Mountains, Jamaica. Methods: Censuses of trees ≥ 3 cm DBH in permanent plots in four sites within ca. 7 ha; 1974–2004 (intensive sites) and in 16 plots within 250 ha; 1990–2004 (extensive plots). Results: Pittosporum was unrecorded in the intensive sites before a severe hurricane in 1988: by 2004 all four sites were invaded. Pittosporum had invaded 25% of the extensive plots in 1990 and 69% in 2004, where its basal area increased from 0.5 ± 0.4 (SEM) m2.ha−1 in 1990 to 2.8 ± 1.3 m2.ha−1 in 2004. It had zero stem mortality and diameter growth rate exceeded that of native species fourfold. Pittosporums basal area in the extensive plots in 2004 was positively related to the stand basal area damaged in the 1988 hurricane and negatively related to soil N concentrations. Pittosporum invasion was unrelated to stand-level tree species diversity in the extensive plots but as its basal area increased over time the basal area of native species and stand-level diversity declined. Conclusions: There are no obvious functional attributes of Pittosporum unrepresented in the native tree flora although it has high photosynthetic efficiency compared with native trees. More widespread invasion of these forests by Pittosporum seems inevitable since hurricanes, which accelerated the invasion, affect these forests frequently. Nomenclature: Adams (1972) except where other authorities given.

IMMEDIATE DAMAGE BY AN EARTHQUAKE TO A TEMPERATE MONTANE FOREST

We quantified the immediate impact of an earthquake (magnitude index MW 6.7 in 1994) on a mountain beech (Nothofagus solandri var. cliffortioides) forest in the Southern Alps, New Zealand. Data from randomly located permanent plots (20 × 20 m) established in 1970 were used to determine the patterns and causes of damage. These plots were located 10 km southeast of the epicenter (Basin Creek, 28 plots in 920 ha) and 30 km southeast of the epicenter (Broken River, 34 plots in 2060 ha). Assessments of earthquake-induced damage in 1995 showed 24.0 ± 5.9% tree mortality and 22.5 ± 4.0% tree injury on Basin Creek plots (all values mean ± 1 se), but only 0.6 ± 0.2% tree mortality and 3.3 ± 1.1% tree injury on Broken River plots. As a result, stem biomass declined from 149 ± 13.8 Mg/ha in 1993 to 114 ± 15.3 Mg/ha in 1995 on Basin Creek plots. On average, earthquake-induced landslides caused 74% of the total stem biomass mortality, and such mortality was greatest on steep slopes. Low-intensity stem biomass mortalit...

Prioritizing species, pathways, and sites to achieve conservation targets for biological invasion

Prioritization is indispensable for the management of biological invasions, as recognized by the Convention on Biological Diversity, its current strategic plan, and specifically Aichi Target 9 that concerns invasive alien species. Here we provide an overview of the process, approaches and the data needs for prioritization for invasion policy and management, with the intention of informing and guiding efforts to address this target. Many prioritization schemes quantify impact and risk, from the pragmatic and action-focused to the data-demanding and science-based. Effective prioritization must consider not only invasive species and pathways (as mentioned in Aichi Target 9), but also which sites are most sensitive and susceptible to invasion (not made explicit in Aichi Target 9). Integrated prioritization across these foci may lead to future efficiencies in resource allocation for invasion management. Many countries face the challenge of prioritizing with little capacity and poor baseline data. We recommend a consultative, science-based process for prioritizing impacts based on species, pathways and sites, and outline the information needed by countries to achieve this. This should be integrated into a national process that incorporates a broad suite of social and economic criteria. Such a process is likely to be feasible for most countries.

Root traits are multidimensional: specific root length is independent from root tissue density and the plant economic spectrum

Summary Root, stem and leaf traits are thought to be functionally coordinated to maximize the efficiency of acquiring and using limited resources. However, evidence is mixed for consistent whole-plant trait coordination among woody plants, and we lack a clear understanding of the adaptive value of root traits along soil resource gradients. If fine roots are the below-ground analogue to leaves, then low specific root length (SRL) and high tissue density should be common on infertile soil. Here, we test the prediction that root, stem and leaf traits and relative growth rate respond in unison with soil fertility gradients. We measured fine root, stem and leaf traits and relative growth rate on individual seedlings of 66 tree species grown in controlled conditions. Our objectives were (i) to determine whether multiple root traits align with growth rate, leaf and stem traits and with each other and (ii) to quantify the relationships between community-weighted mean root traits and two strong soil fertility gradients that differed in spatial extent and community composition. At the species level, fast growth rates were associated with low root and stem tissue density and high specific leaf area. SRL and root diameter were not clearly related to growth rate and loaded on a separate principal component from the plant economic spectrum. At the community level, growth rate was positively related to soil fertility, and root tissue density (RTD) and branching were negatively related to soil fertility. SRL was negatively related and root diameter was positively related to soil fertility on the large-scale gradient that included ectomycorrhizal angiosperms. Synthesis. Root, stem and leaf tissue traits of tree seedlings are coordinated and influence fitness along soil fertility gradients. RTD responds in unison with above-ground traits to soil fertility gradients; however, root traits are multidimensional because SRL is orthogonal to the plant economic spectrum. In contrast to leaves, trees are not constrained in the way they construct fine roots: plants can construct high or low SRL roots of any tissue density. High RTD is the most consistent below-ground trait that reflects adaptation to infertile soil.

Plant characteristics are poor predictors of microsite colonization during the first two years of primary succession

Abstract Questions: Do plant characteristics predict microsite colonization in severe habitats dominated by abiotic factors? Specifically, does colonization of microsites differ among shrubs, forbs and grasses or between wind- and water-dispersed plants, non-native and native plants, or N-fixing and non-N-fixing plants? Location: Kowhai River floodplain, Kaikoura, South Island, New Zealand. Methods: Five microsite characteristics were measured for > 1000 individuals representing 27 colonizing plant species on a two-year old surface of a primary succession on a New Zea-land floodplain. The microsite characteristics included surface contour (convex, concave, or flat), the position of the plant (e.g., upstream, downstream) relative to the closest rock with > 20 cm maximum dimension, the distance to that same rock, the depth of the base of the stem below the surface of a plane resting on the adjacent microrelief, and soil particle size (gravel, pebbles or sand). Results: All plants preferred concave microsites near large rocks relative to systematically placed null points. We found no clear preferences for microhabitats by dispersal mode, native vs. non-native status, or plants with or without nitrogen-fixing symbionts, but grasses preferentially colonized fine soil particles. Highly variable responses among species contributed to these results. Better predictability of microsite preference was obtained for individual species than for plants grouped by characteristics. Conclusions: Our results suggest that in severe habitats with strong abiotic filters and low microsite availability, such as found in early primary succession, coarse categories of species characteristics are poor predictors of colonization success. Nomenclature: Allan (1961) with amendments suggested by Connor & Edgar (1987); Webb et al. (1988); Edgar & Connor (2000).

Promotion of ecosystem carbon sequestration by invasive predators

Despite recent interest in understanding the effects of human-induced global change on carbon (C) storage in terrestrial ecosystems, most studies have overlooked the influence of a major element of global change, namely biological invasions. We quantified ecosystem C storage, both above- and below-ground, on each of 18 islands off the coast of New Zealand. Some islands support high densities of nesting seabirds, while others have been invaded by predatory rats and host few seabirds. Our results show that, by preying upon seabirds, rats have indirectly enhanced C sequestration in live plant biomass by 104%, reduced C sequestration in non-living pools by 26% and increased total ecosystem C storage by 37%. Given the current worldwide distribution of rats and other invasive predatory mammals, and the consequent disappearance of seabird colonies, these predators may be important determinants of ecosystem C sequestration.