Native diversity buffers against severity of non-native tree invasions

Determining the drivers of non-native plant invasions is critical for managing native ecosystems and limiting the spread of invasive species1,2. Tree invasions in particular have been relatively overlooked, even though they have the potential to transform ecosystems and economies3,4. Here, leveraging global tree databases5–7, we explore how the phylogenetic and functional diversity of native tree communities, human pressure and the environment influence the establishment of non-native tree species and the subsequent invasion severity. We find that anthropogenic factors are key to predicting whether a location is invaded, but that invasion severity is underpinned by native diversity, with higher diversity predicting lower invasion severity. Temperature and precipitation emerge as strong predictors of invasion strategy, with non-native species invading successfully when they are similar to the native community in cold or dry extremes. Yet, despite the influence of these ecological forces in determining invasion strategy, we find evidence that these patterns can be obscured by human activity, with lower ecological signal in areas with higher proximity to shipping ports. Our global perspective of non-native tree invasion highlights that human drivers influence non-native tree presence, and that native phylogenetic and functional diversity have a critical role in the establishment and spread of subsequent invasions

Integrated global assessment of the natural forest carbon potential

Forests are a substantial terrestrial carbon sink, but anthropogenic changes in land use and climate have considerably reduced the scale of this system1. Remote-sensing estimates to quantify carbon losses from global forests2,3,4,5 are characterized by considerable uncertainty and we lack a comprehensive ground-sourced evaluation to benchmark these estimates. Here we combine several ground-sourced6 and satellite-derived approaches2,7,8 to evaluate the scale of the global forest carbon potential outside agricultural and urban lands. Despite regional variation, the predictions demonstrated remarkable consistency at a global scale, with only a 12% difference between the ground-sourced and satellite-derived estimates. At present, global forest carbon storage is markedly under the natural potential, with a total deficit of 226 Gt (model range = 151–363 Gt) in areas with low human footprint. Most (61%, 139 Gt C) of this potential is in areas with existing forests, in which ecosystem protection can allow forests to recover to maturity. The remaining 39% (87 Gt C) of potential lies in regions in which forests have been removed or fragmented. Although forests cannot be a substitute for emissions reductions, our results support the idea2,3,9 that the conservation, restoration and sustainable management of diverse forests offer valuable contributions to meeting global climate and biodiversity targets

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees

New horizons in sustainable small-scale forestry

Preceding chapters have illustrated the multitude of objectives and wide variety of forms which small-scale forestry can take. We now seek to draw together some of the themes developed. Impediments to small-scale forestry are examined, and forest policies for achieving maximum benefits are discussed. Small-scale forestry is viewed as not simply a scaled-down version of industrial forestry, but a vibrant industry sector with great diversity in forestry systems and objectives. Notable developments and innovations are taking place in small-scale forestry

Assessing financial performance of small-scale forestry

[Extract] This chapter discusses some of the key issues associated with assessment of the financial performance of small-scale plantations. Issues discussed include choice of financial performance indicators, modelling of tree growth for nontraditional species, and price and marketing considerations. The development of financial models for small-scale mixed-species plantations established under the Community Rainforest Reforestation Program (CRRP) in north Queensland provides a case study of how models may be developed when there is a lack of empirical data

Choice of timber inputs by small to medium sized cabinet-making firms in Queensland and implications for the marketing of lesser-known tropical species

[Extract] This chapter discusses the marketing of tropical rainforest cabinet timbers, particularly in relation to small to medium sized cabinet-making firms. While this analysis is set in context of Queensland firms and Australian rainforest and eucalypt species, many of the principles can be applied to other tropical species. Price only becomes important when it cannot be passed on to the purchaser. Australian rainforest cabinet timbers are highly regarded by both cabinet-makers and the general public; however, their use is restricted by actual and perceived availability. Queensland maple, red cedar and northern silky oak are the rainforest species most highly recommended by cabinet-makers for planting to satisfy their future timber requirements

The role of portable sawmills and chainsaw milling in tropical small-scale forestry

Various forms of portable or 'walkabout' sawmills have become popular for timber extraction and in-forest milling in tropical forestry in recent years. A number of advantages over larger fixed-site mills have been recognised, such as reduced transport costs and utilisation of smaller logs and branches. Portable bandsaws, with a thin blade kerf generally give rise to a greater timber recovery than traditional circular saws. Chainsaws have been criticised for greater timber wastage, and in some cases their use for timber extraction has been declared illegal. The choice of appropriate technology involves a tradeoff with respect to various factors including capital outlays, maintenance capability and costs, labour efficiency and timber recovery rate. If these items are factored into the overall average cost curve, it becomes apparent that both portable sawmills and chainsaw milling do have an important role in tropical small-scale forestry. the latter are particularly useful for flitch cutting as a first stage of milling

Small-scale forestry systems for timber and non-timber benefits including biodiversity

[Extract] Forestry systems produce a diverse range of services, which need to be viewed within a societal context. This chapter addresses the interaction between the biological nature of plantations forests (and their design) and the important interactions with social and economic issues which directly affect or are affected by the structure of planting systems. Various systems are available at a small-scale level and they can be manipulated to produce different mixes of timber and non-timber products and tradeoffs

Sustainable small-scale forestry in the Philippines

[Extract] The Philippines with a large population and low per-capita income faces severe pressure on its residual forest resources and has a recent history of rapid deforestation. Various policy initiatives have been introduced topromote reforestation, with low levels of success. Timber marketing and milling was a major component of the Philippine economy until recently when changes in government policy reduced the volume of logging in native forests. Because of this shortage, the use of coco lumber has expanded. This chapter discusses forest industries and stakeholders in the Philippines, and in particular farm, social and community forestry systems. There are a number of impediments to all forms of reforestation. Government policy has moved from mainly supporting industrial and large-scale planting schemes to also promoting community forestry