Forest biodiversity, ecosystem functioning and the provision of ecosystem services

Forests are critical habitats for biodiversity and they are also essential for the provision of a wide range of ecosystem services that are important to human well-being. There is increasing evidence that biodiversity contributes to forest ecosystem functioning and the provision of ecosystem services. Here we provide a review of forest ecosystem services including biomass production, habitat provisioning services, pollination, seed dispersal, resistance to wind storms, fire regulation and mitigation, pest regulation of native and invading insects, carbon sequestration, and cultural ecosystem services, in relation to forest type, structure and diversity. We also consider relationships between forest biodiversity and multifunctionality, and trade-offs among ecosystem services. We compare the concepts of ecosystem processes, functions and services to clarify their definitions. Our review of published studies indicates a lack of empirical studies that establish quantitative and causal relationships between forest biodiversity and many important ecosystem services. The literature is highly skewed; studies on provisioning of nutrition and energy, and on cultural services, delivered by mixed-species forests are under-represented. Planted forests offer ample opportunity for optimising their composition and diversity because replanting after harvesting is a recurring process. Planting mixed-species forests should be given more consideration as they are likely to provide a wider range of ecosystem services within the forest and for adjacent land uses. This review also serves as the introduction to this special issue of Biodiversity and Conservation on various aspects of forest biodiversity and ecosystem services

Insights from full-rotation Nelder spacing trials with Eucalyptus in São Paulo, Brazil

The choice of spacing among trees for operational plantations is typically based on one or more experimental plantations that test for the response of tree and stand growth to a range of tree-to-tree distances. The most common design for spacing experiments entails rectangular plots that test different distances between rows, and between trees within rows, and with replication of plots covering one to several hectares within a single stand. Other designs may offer more information with simpler layouts, and we examined the insights that could be obtained from a Nelder (fan-shape) design, where spacing among trees varies with the radial distance from a central point. The response of Eucalyptus dunnii seed-origin trees to spacing was essentially similar between a classic plot design replicated in four blocks (tree spacing from 4.5 to 9.2 m2 tree-1, covering 1.4 ha of land), and a  Nelder design (tree spacing from 2.1 to 44.0 m2 tree-1, covering 0.6 ha of land). The Nelder design showed slightly higher volume increment  through 10 years of stand development than the block design (for the  range of overlap in spacing), but the treatment effect of spacing was essentially identical between the designs at the level of both trees and stands. A second Nelder experiment used clonal-origin trees from six clones, testing for differences in responses to spacing among clones. In all three spacing experiments and for all clones, individual-tree growth was greatest at the widest spacing and stand-level growth was highest at the tightest spacing. These trends were much clearer across the wider range of spacing tested in the Nelder plots (228 to 4 760 trees ha-1) than in the narrower range of spacing tested in the block design (1 111 to 2 222 trees ha-1). Current annual increment reached a higher, earlier peak at narrow spacing. At 8.5 years, the light use efficiency (stem volume growth per unit of light intercepted) was about twice as great for trees at narrow spacing than at wider spacing. Overall, the Nelder designs provided the same information on responses to spacing as the classic block design. The simplicity and small size of Nelder designs provide valuable insights for basic decisions on spacing for operational plantations, particularly when forestry extends into new geographic areas, new genotypes, and new silvicultural techniques. Keywords: Eucalyptus clones, Eucalyptus dunnii, forest growth and yield, leaf area, light use efficiency, sawlog productionSouthern Forests 2010, 72(2): 90–9

Productivity gains by fertilisation in Eucalyptus urophylla clonal plantations across gradients in site and stand conditions

Nutrition management in Eucalyptus plantations is fundamental for sustaining high production. Fertilisation is routinely used to improve tree nutrition, providing profitable returns on large investments. Growth responses to fertilisation differ dramatically among sites, however, so efficient investment decisions in fertilisation is important. The twin-plots  design characterises the fertilisation response in a short period of time, providing the information needed to landscape-scale silvicultural prescriptions. This method entails the establishment of pairs of plots, with one control and one treated plot at each location. The control plot may typically be a permanent plot of an inventory network, providing representative information for a company’s decisionmaking. The paired twin-plot receives intensive management (high fertilisation and weed control) to minimise (or remove) these constraints to forest productivity. We used this approach with 131 blocks of twin-plots to represent an area of 34 540 ha in the state of São Paulo, Brazil. Clonal plantations of Eucalyptus urophylla were remeasured one and two years after treatment. Fertilisation increased wood growth by 15% for two years (4.0 t ha–1 y–1, or 8.1 m3 ha–1 y–1), with the current annual biomass increment reaching 31.6 t ha–1 y–1 (64.2 m3 ha–1 y–1) versus 27.6 t ha–1 y–1 (56.1 m3 ha–1 y–1) of the control plots. Twin-plots located on sandier and less fertile soils showed twice the fertilisation response of other plots, increasing wood growth by 8.5 t ha–1 y–1 (16.9 m3 ha–1 y–1). The two predominant clones responded similarly to fertilisation. Older stands showed higher responses than younger stands (1.7 t ha–1 y–1 for each additional year), and the greater response in older stands  probably represented increase in fertilisation rates over time, rather than a feature of the age of the stands per se. Fertilisation response correlated negatively with site index (base age 7), soil clay content, and soil base nutrient levels (Ca, Mg and K). Models for the prediction of fertilisation response can be used to develop regional- and site-specific fertiliser prescriptions to maximise financial gain from fertilisation. Keywords: Eucalyptus urophylla; fertilisation; intensive silviculture; inventory network; tropical plantations; twin-plotsSouthern Forests 2009, 71(4): 253–25

Why don\'t our stands grow even faster? Control of production and carbon cycling in eucalypt plantations

The growth of Eucalyptus stands varies several fold across sites, under the influence of resource availability, stand age and stand structure. We describe a series of related studies that aim to understand the mechanisms that drive this great range in stand growth rates. In a seven-year study in Hawaii of Eucalyptus saligna at a site that was not water limited, we showed that nutrient availability differences led to a two-fold difference in stand wood production. Increasing nutrient supply in mid-rotation raised productivity to the level attained in continuously fertilised plots. Fertility affected the age-related decline in wood and foliage production; production in the intensive fertility treatments declined more slowly than in the minimal fertility treatments. The decline in stem production was driven largely by a decline in canopy photosynthesis. Over time, the fraction of canopy photosynthesis partitioned to below-ground allocation increased, as did foliar respiration, further reducing wood production. The reason for the decline in photosynthesis was uncertain, but it was not caused by nutrient limitation, a decline in leaf area or in photosynthetic capacity, or by hydraulic limitation. Most of the increase in carbon stored from conversion of the sugarcane plantation to Eucalyptus plantation was in the above-ground woody biomass. Soil carbon showed no net change. This study and other studies on carbon allocation showed that resource availability changes the fraction of annual photosynthesis used below-ground and for wood production. High resources (nutrition or water) decrease the partitioning below-ground and increase partitioning to wood production. Annual foliage and wood respiration and foliage production as a fraction of annual photosynthesis was remarkably constant across a wide range of fertility treatments and forest age. In the Brazil Eucalyptus Productivity Project, stand structure was manipulated by planting clonal Eucalyptus all at once or in three groups at three-monthly intervals, producing a stand where trees did not segregate into dominants and one that had strong dominance. The uneven stand structure reduced production 10–15% throughout the rotation. Keywords: age-related productivity decline; carbon allocation; forest production ecology; nutritionSouthern Forests 2008, 70(2): 99–10

Assessing the effects of early silvicultural management on long-term site productivity of fast-growing eucalypt plantations: the Brazilian experience

Eucalyptus is the dominant and most productive planted forest in Brazil, covering around 3.4 million ha for the production of charcoal, pulp, sawtimber, timber plates, wood foils, plywood and for building purposes. At the early establishment of the forest plantations, during the second half of the 1960s, the eucalypt yield was 10 m3 ha–1 y–1. Now, as a result of investments in research and technology, the average productivity is 38 m3 ha–1 y–1. The productivity restrictions are related to the following environmental factors, in order of importance: water deficits > nutrient deficiency > soil depth and strength. The clonal forests have been fundamental in sites with larger water and nutrient restrictions, where they out-perform those established from traditional seed-based planting stock. When the environmental limitations are small the productivities of plantations based on clones or seeds appear to be similar. In the long term there are risks to sustainability, because of the low fertility and low reserves of primary minerals in the soils, which are, commonly, loamy and clayey oxisols and ultisols. Usually, a decline of soil quality is caused by management that does not conserve soil and site resources, damages soil physical and chemical characteristics, and insufficient or unbalanced fertiliser management. The problem is more serious when fast-growing genotypes are planted, which have a high nutrient demand and uptake capacity, and therefore high nutrient output through harvesting. The need to mobilise less soil by providing more cover and protection, reduce the nutrient and organic matter losses, preserve crucial physical properties as permeability (root growth, infiltration and aeration), improve weed control and reduce costs has led to a progressive increase in the use of minimum cultivation practices during the last 20 years, which has been accepted as a good alternative to keep or increase site quality in the long term. In this paper we provide a synthesis and critical appraisal of the research results and practical implications of early silvicultural management on long-term site productivity of fast-growing eucalypt plantations arising from the Brazilian context.Keywords: fertilisation; minimum cultivation; residue management; soil preparation; sustainability; water deficitSouthern Forests 2008, 70(2): 105–11

Assessing the effects of early silvicultural management on long-term site productivity of fast-growing eucalypt plantations: the Brazilian experience

International audienceEucalyptus is the dominant and most productive planted forest in Brazil, covering around 3,4 million ha for the production of charcoal, pulp, sawtimber, timber plates, wood foils, plywood and for building purposes. At the early establishment of the forest plantations, during the second half of the 1960s, the eucalypt yield was 10 m3 ha-1 y-1 . Now, as a result of investments in research and technology, the average productivity is 38 m3 ha-1 y-1. The productivity restrictions are related to the following environmental factors, in order of importance: water deficits > nutrient deficiency > soil depth and strength. The clonal forests have been fundamental in sites with larger water and nutrient restrictions, where they out-perform those established from traditional seed-based planting stock. When the environmental limitations are small the productivities of plantations based on clones or seeds appear to be similar. In the long term there are risks to sustainability, because of the low fertility and low reserves of primary minerals in the soils, which are, commonly, loamy and clayey oxisols and ultisols. Usually, a decline of soil quality is caused by management that does not conserve soil and site resources, damages soil physical and chemical characteristics, and insufficient or unbalanced fertiliser management. The problem is more serious when fast-growing genotypes are planted, which have a high nutrient demand and uptake capacity, and therefore high nutrient output through harvesting. The need to mobilise less soil by providing more cover and protection, reduce the nutrient and organic matter losses, preserve crucial physical properties as permeability (root growth, infiltration and aeration), improve weed control and reduce costs has led to a progressive increase in the use of minimum cultivation practices during the last 20 years, which has been accepted as a good alternative to keep or increase site quality in the long term. In this paper we provide a synthesis and critical appraisal of the research results and practical implications of early silvicultural management on long-term site productivity of fast-growing eucalypt plantations arising from the Brazilian context