Will Livestock Intensification Help Save Latin America's Tropical Forests?

ABSTRACT

Researchers have long argued that improved livestock technologies and intensification will reduce the pressure on Latin America's forests. This article combines economic theory with insights from seven case studies to examine under what conditions technological change will reduce (or increase) forest clearing. In many contexts improved technologies—by making cattle production more profitable—will result in more forest being converted to pasture. Silvopastoral systems and other labor-intensive practices can restrain pasture expansion, at least in the short-run. Unfortunately, in most cases ranchers will only be willing to adopt such land-saving practices when land has become scarce and most of the forest is gone.     

How Can We Incentivize Tropical Forest Restoration?

International policy incentives to promote tropical forest restoration, community forestry, and payments for environmental services have not been widely adopted at scale. It is possible that reducing emissions from deforestation and forest degradation and related activities (REDD+) could be a policy tool for encouraging larger scale restoration efforts in the tropics. Although there are political challenges to ensuring the inclusion of restoration activities in REDD+, its use might facilitate the forest transition in tropical countries, reduce carbon dioxide concentrations in the atmosphere, and garner political support for these policies and approaches.     

Can oil palm plantations become bird friendly?

Despite the increasing claims that structural complexity in agroforestry plantations is a key variable for enhancing bird biodiversity, few studies have experimentally manipulated the understory component of structural complexity. Here, we examined the impact of removing understory vegetation from oil palm plantations on the richness and abundance of birds in eastern Guatemala, testing if bird richness and abundance are positively affected by the presence of understory vegetation. Oil palm plantations with understory hold more bird richness and abundance than those lacking it. The experimental removal of this vegetation, equivalent to a reduction in complexity, decreases bird richness but not abudance. Our analysis shows clear effects of vegetation removal on bird richness, such that removal reduces richness and abundance to levels found in areas without understory. Hence, leaving or implementing structural complexity within plantations could satisfy the current need of making commodity production a cleaner industry, fulfilling both, the production of highly demanded commodities and the conservation of biodiversity in productive landscapes. Oil palm (Elaeis guineensis) is one of the most rapidly expanding crop in tropical regions, representing the major cause of loss of natural forests and of the decline of endangered species in several countries. Enhancing understory vegetation might reduce such negative effects. This is one of the few experimental tests about how a component of the vegetation and structural complexity of plantations affects birds.     

Can distribution of trees explain variation in nitrous oxide fluxes?

Abstract

The impact of distance to tree stems on nitrous oxide (N₂O) fluxes was examined to determine whether it is possible to improve the accuracy of flux estimates from boreal forest soils. Dark static chambers were placed along transects between pairs of trees within a Norway spruce stand and fluxes of N₂O and carbon dioxide (CO₂) were measured during the period 1999–2003. The groundwater table was measured on every sampling occasion along the transects. In addition, radiation transmission, potential diffusion rate and biomass of forest floor vegetation were measured once at each chamber site along one of the transects and soil samples were collected at three depths, from which pH, denitrification enzyme activity, soil moisture, organic matter, and carbon and nitrogen content were determined. There was a high level of variation in the N₂O fluxes, both spatially and temporally. However, the spatial variation in the N₂O fluxes within the transect could not be explained by differences in any of the measured variables. Sometimes, mainly when no major peaks occurred, N₂O fluxes were significantly correlated with CO₂ release. It is concluded that distance to stems cannot be used to improve the design of sampling schemes or for extrapolating flux levels to larger scales.     

Can small-scale altitudinal gradients predict spatial and temporal patterns in tropical forests?

In tropical montane forests,compositional and structural changes are commonly driven by broad-scale altitudinal variation.Here,given the lack of knowledge on small-scale vegetation changes and temporal dynamics,we address the effects of small-scale variations in soil and altitude on tree community structure,temporal dynamics and phylogenetic diversity in a semi-deciduous tropical forest of the Atlantic Forest Domain,southeastern Brazil.In 2010 and 2015 we sampled thirty plots of 400 m~2,set up along an altitudinal gradient between 1000 and 1500 m a.s.I..In each plot,we collected soil samples for chemical and textural analyses.We fitted linear models to test the effects of altitude and soil on community dynamics and phylogenetic parameters.Altitude and soil explained the spatial variation in number of individuals and phylogenetic diversity metrics.From lower to higher altitudes,we found decreasing fertility,increasing tree density and decreasing phylogenetic diversity.Altitude significantly influenced the increases in total biomass(from 240.9 to 255.4 t ha~(-1)) and individual biomass(from 0.15 to 0.17 t) recorded in the interval.And while community temporal dynamics had rates of 1.96% for mortality,1.02% for recruitment,1.61% for biomass loss and 2.81% for biomass gain,none of them were explained by altitude or soil.Temporal species substitution averaged0.1 in the interval.Altogether,these results suggest that the small-scale variations in altitude and soil likely determine the conditions and resources that drive community assembly and structure,which are expressed by spatial variations along the altitudinal gradient.At the same time,temporal patterns were not influenced by altitude-related environmental variation,resulting in a similar dynamic behaviour across the gradient,suggesting that broad-scale factors may play a more important role than local ones.     

Can native vegetation recover after slash pine cultivation in the Brazilian Savanna?

There is a widespread view that forest plantations with exotic species are green deserts, unable to sustain biodiversity. Few studies have demonstrated, however, that planted stands of exotic trees have a greater negative effect on the plant diversity of savanna vegetation. We compared the native woody flora under four stands of slash pine of about 45 years old with four stands where the previously existing native Cerrado vegetation was preserved and protected from disturbances for the same period, has changed into dense vegetation - the “cerradão”, at Assis municipality, São Paulo State, Brazil. Aiming at understanding the potential ecological filters driving these communities, we assessed air and soil humidity, light availability and classified the native species on the basis of shade tolerance, dispersal syndrome and biomes in which they occur (Atlantic Forest or Cerrado). We recorded an average of 70 (±13) species under pine stands and 54 (±16) species in cerradão. Of the total of 136 species recorded, 78 occurred in both habitats, eight were exclusive to the “cerradão” (shade tolerant and also occurring in forest ecosystems) and 18 were recorded only under pine stands (82% heliophytic, exclusive to the Cerrado biome). Among the functional attributes and abiotic variables analyzed, only light availability explained the floristic differences found. Since richness was higher under pine, we refuted the hypothesis that exotic species constrain the establishment of the native species richness in the understory. On the other hand, the dark environment under the closed-canopy of the “cerradão” acts as a filter inhibiting the establishment of typical Cerrado species. Since pine stands, if managed in long cycle, maintain a reasonable pool of Cerrado endemic species in the understory pine plantations may be a good starting point for savanna restoration.     

Can the ecosystem mimic hypotheses be applied to farms in African savannahs?

The first ecosystem mimic hypothesis suggests clear advantages if man-made land use systems do not deviate greatly in their resource use patterns from natural ecosystems typical of a given climatic zone. The second hypothesis claims that additional advantages will accrue if agroecosystems also maintain a substantial part of the diversity of natural systems. We test these hypotheses for the savannah zone of sub-Saharan Africa, with its low soil fertility and variable rainfall. Where annual food crops replace the natural grass understorey of savannah systems, water use will decrease and stream and groundwater flow change, unless tree density increases relative to the natural situation. Increasing tree density, however, will decrease crop yields, unless the trees meet specific criteria. Food crop production in the parkland systems may benefit from lower temperatures under tree canopies, but water use by trees providing this shade will prevent crops from benefiting. In old parkland trees that farmers have traditionally retained when opening fields for crops, water use per unit shade is less than in most fast growing trees introduced for agroforestry trials. Strong competition between plants adapted to years with different rainfall patterns may stabilise total system productivity -- but this will be appreciated by a farmer only if the components are of comparable value. The best precondition for farmers to maintain diversity in their agroecosystem hinges on the availability of a broad basket of choices, without clear winners or 'best bets'. This revised version was published online in June 2006 with corrections to the Cover Date.     

Can Eucalyptus invade native forest fragments close to commercial stands?

Some Eucalyptus species are widely used as a plantation crop in tropical and subtropical regions. One reason for this is the diversity of end uses, but the main reason is the high level of wood production obtained from commercial plantings. With the advancement of biotechnology it will be possible to expand the geographical area in which eucalypts can be used as commercial plantation crops, especially in regions with current climatic restrictions. Despite the popularity of eucalypts and their increasing range, questions still exist, in both traditional planting areas and in the new regions: Can eucalypts invade areas of native vegetation, causing damage to natural ecosystems biodiversity?The objective of this study it was to assess whether eucalypts can invade native vegetation fragments in proximity to commercial stands, and what factors promote this invasive growth. Thus, three experiments were established in forest fragments located in three different regions of Brazil. Each experiment was composed of 40 plots (1 m² each one), 20 plots located at the border between the forest fragment and eucalypts plantation, and 20 plots in the interior of the forest fragments. In each experimental site, the plots were paired by two soil exposure conditions, 10 plots in natural conditions and 10 plots with soil exposure (no plant and no litter). During the rainy season, 2 g of eucalypts seeds were sown in each plot, including Eucalyptus grandis or a hybrid of E. urophylla × E. grandis, the most common commercial eucalypt species planted in the three region. At 15, 30, 45, 90, 180, 270 and 360 days after sowing, we assessed the number of seedlings of eucalypts and the number of seedlings of native species resulting from natural regeneration. Fifteen days after sowing, the greatest number of eucalypts seedlings (37 m⁻²) was observed in the plots with lower luminosity and exposed soil. Also, for native species, it was observed that exposed soil improved natural germination reaching the highest number of 163 seedlings per square meter. Site and soil exposure were the factors that have the greatest influence on seed germination of both eucalypt and native species. However, 270 days after sowing, eucalypt seedlings were not observed at any of the three experimental sites. The result shows the inability of eucalypts to adapt to condition outside of their natural range. However, native species demonstrated their strong capacity for natural regeneration in forest fragments under the same conditions where eucalypts were seeded.     

Managing watershed services of tropical forests and plantations: Can meta-analyses help?

The watershed services provided by tropical natural and planted forests are critical to human well-being. An increasing number of valuation studies and experiences with payment for ecosystem services have dealt with the role of ecosystems in regulating the flow of water. However, several studies and experiences have been based on misconceptions about the role of forests and plantations in the hydrological cycle, despite the publication of many reviews by hydrologists. The objective of this paper is to evaluate whether meta-analyses applied to studies comparing water flows in tropical watersheds under natural or planted forests and non-forest lands can provide useful results for valuing watershed ecosystem services and making decisions. The meta-analyses show significantly lower total flows or base flows under planted forests than non-forest land uses. Meta-analyses conducted with subsamples of the data also show lower total flow and higher base flow under natural forests than non-forest land uses. However, the available studies were restricted to humid climates and particular forest types (Pinus and Eucalyptus planted forests and lowland natural forests). The small number of available studies with sufficient original data is a major constraint in the application of meta-analyses. This represents a major technical challenge for valuation studies or payment for ecosystem services, especially in countries where financial resources for implementing field research are scarce.     

Can plot edge bias be reduced by means of airborne laser scanning?

This paper presents new methods for plot edge bias (PEB) correction of individual tree competition indices (CIs) using airborne laser scanning (ALS) as auxiliary information in multivariate ratio and multivariate regression models. I applied the methods to 557 plots from the Norwegian National Forest Inventory located in Hedmark County in South East Norway and compared them to the benchmarks methods linear expansion and simulated annealing by studying the individual tree growth predictions before and after PEB correction. Generally, the simulated annealing method seemed to improve growth prediction most and overall the existing methods performed better than those based on ALS. All PEB-correction methods tested gave minor changes in growth predictions and the absolute change in percent in adj. R² and Akaike's Information Criterion (AIC) was numerically small, with an average percentage change for the tested CIs between 1.8 for adj. R² and 0.6 for AIC of the observed values in the original data. The small differences in the results between the original data and the PEB-corrected data show that on average PEB remains a minor problem for individual tree growth prediction. Whether the results are valid for forests with significantly different spatial composition than that of this database remains to be confirmed.     

Can Hymenoscyphus fraxineus infect hardy members of the Oleaceae other than ash species?

The interaction between the ash dieback fungus, Hymenoscyphus fraxineus, and two commonly grown members of the Oleaceae (Forsythia × intermedia ‘Lynwood’ and Ligustrum vulgare) was investigated. Shoots were inoculated with three isolates of H. fraxineus and harvested after 2 and 10 weeks. DNA was extracted from tissue collected at the point of inoculation, as well as 15 mm below and above (distal), and analysed using fungal‐specific ITS primers and specific primers for H. fraxineus. The fungus was frequently detected in tissue at the point of inoculation, but rarely in distal samples. There was no evidence that H. fraxineus was pathogenic on either of the two oleaceous species over the duration of the experiment.     

Can we use shelterwoods in Mediterranean pine forests to promote oak seedling development?

The use of shelterwoods to favour the development of natural or underplanted seedlings is common in temperate forests but rare in the pine forests of the Mediterranean area. Our aim was to assess the use of shelterwoods in Aleppo pine (Pinus halepensis) woodlands in southern France to promote the survival and growth of two co-occurring oak species: the deciduous Quercus pubescens and the evergreen Quercus ilex.Twelve Aleppo pine stands were selected and differentially thinned to create a light shelterwood (basal area = 10 m²/ha, irradiance 52%), a medium shelterwood (basal area = 19 m²/ha, irradiance 33%) and a dense shelterwood (basal area = 32 m²/ha, irradiance 13%). A total of 1248 sowing points, half composed of Q. pubescens and half of Q. ilex, were then set up in these three conditions. Seedling survival and growth were monitored for 3 years. Plant stress was assessed by measuring predawn leaf potential and photosynthetic performance through the F_v/F_m ratio. Soil moisture was also recorded at two depths during two growing seasons.Survival was high for both species in all three conditions due to three consecutive wet years. The lowest survival was recorded for Q. pubescens in the dense shelterwoods. Growth in diameter and height increased from the dense to the light shelterwoods. Shrubs developed more strongly in the light shelterwood, and increasing shrub cover enhanced height growth. Photosynthetic performance was lowest for Q. pubescens in dense shelterwoods and highest in light shelterwoods, whereas the reverse was true for Q. ilex. The lowest predawn potentials were recorded in the dense shelterwoods even though higher soil water content values were measured in this treatment during the summer drought.We show that light shelterwoods were more beneficial to growth than denser ones, indicating control mainly by light availability during the 3 years of the study. However, as lower soil moisture at 30-50 cm depth and faster understorey development were also recorded in this condition, more extended observation is needed to determine whether this benefit persists in subsequent years.     

Can birds play a role as High Nature Value indicators of montado system?

Montados form a heterogeneous landscape of wooded matrix dominated by cork and/or holm oak with open areas characterized by fuzzy boundaries. Montado supports a high biological diversity associated to low intensity management and a landscape diversity provided by a continuous gradient of land cover. Among other features this permits the classification of montados as a High Nature Value (HNV) system. We assessed the role of birds as HNV indicators for montado, and tested several bird groups—farmland, edge, forest generalists and forest specialists species; and some universal indicators such as species conservation status, Shannon’s diversity index and species richness. Our study areas covered the North–South distribution of cork oak in Portugal, and we surveyed the breeding bird communities across 117 sampling sites. In addition to variables related to management and sanitary status, we considered variables that characterize the landscape heterogeneity inside the montado—trees and shrub density and richness of woody vegetation. Our results suggest that specific bird guilds can be used as HNV indicators of particular typologies of montado, and highlight the need to develop an indicator that could be transversally applied to all types of montado.     

Can market-based agroforestry germplasm supply systems meet the needs of forest landscape restoration?

By late 2017, governments had pledged more than 140 M ha to the global forest landscape restoration (FLR) agenda. Although much FLR will consist of conventional ecological restoration, a substantial proportion will involve agroforestry. The question therefore arises of how the agroforestry germplasm needs of FLR can be met, particularly given its emphasis on species diversity. This paper examines the role of market-based germplasm supply systems. A simple analytic framework is presented, and key demand- and supply-related factors are described. It is suggested that seedling supply and demand at market prices will not necessarily coincide with needs of all farmers nor with the requirements of a particular restoration program, and that market-based germplasm supply systems will therefore often not meet the needs of restoration programs. Implications of these findings are then identified and appropriate responses are suggested. These include those intended to produce shifts in demand or supply curves through addressing the underlying enabling environment, and direct subsidies to tree planting stock prices.     

Can agricultural management emulate natural ecosystems in recharge control in south eastern Australia?

Water balance information at locations across southern Australia is analysed to identify mechanistic causes for higher water tables under agricultural systems compared to natural vegetation. Contrasting patterns of water use indicate pronounced physiological activity in summer by natural ecosystems ensuring the persistence of the dominant perennial species. A strategy of tempered water use during periods of rainfall excess in winter/spring enables seasonal carryover of soil water to be withdrawn by deep roots for summer functioning. Characteristic patterns of water use by agricultural systems, comprised mainly of determinant annual species, are truncated in time but feature elevated peak rates coinciding with periods of maximum soil water availability during the cooler months. Low seasonal vapour pressure deficit explains the observed benefits of enhanced biomass production due to high water use efficiency. The associated limited scope for soil water uptake carries the penalty of increased frequency of drainage and the subsequent resource degradation currently associated with farmland. Inclusion of a perennial lucerne phase in rotation with crops confers environmental benefit through summer uptake from a rooting depth double that of crops. An effective buffer is thus provided to restrict drainage under an ensuing cropping phase in a manner that more closely emulates natural systems. Simulations of phase farming point to a halving in long term drainage. They suggest adoption over a range of arable land units could cause local retreat of water tables by 0.3 m y⁻¹ initially, leading to a new equilibrium level which would still remain elevated with respect to that under natural vegetation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Landscape-scale disturbance and boreal forest birds: Can large single-pass harvest approximate fires?

Boreal forest birds have adapted to changes caused by natural disturbances such as fire and this adaptation forms the basis for the Natural Disturbance Paradigm (NDP) underlying recent proposed changes in forest harvesting practices in western Canada. To date, this paradigm has been evaluated primarily at the stand level and within conventional harvesting systems. The potential for improvements in avian conservation at the landscape scale by adopting the NDP approach is largely unknown. We examined the effects of landscape-scale disturbances on forest bird communities by contrasting richness and abundance of birds in (1) 16 single-pass harvest sites with residual forest patches, (2) 29 multi-pass harvest sites with residuals; and (3) 15 salvage-logged post-fire sites with variable harvest intensity. We contrasted bird communities in these treatments with those in unsalvaged post-fire sites of similar age. Post-fire sites were used to provide a metric of the Natural Range of Variation (NRV) to be expected in bird communities. Sites were surveyed for avian community composition and abundance 1–5 years post-disturbance. Redundancy analysis indicated that bird communities differed from the NRV in all of the harvest treatments. However, single-pass harvests provided a somewhat better fit to NRV than did multi-pass harvesting. Avian community similarity was influenced by non-linear responses to area harvested, amount of residual retention, residual composition and pre-disturbance forest composition. An optimization routine created from a General Linear Model, suggests that community similarity to NRV can be maximized by using single-pass harvests over multi-pass harvests, harvesting 66–88% of the timber in the planning unit, and retaining 5–19% of the disturbance area as live residual patches, with 50% of harvests having at least 9% of the area in residuals.     

Can native tree species plantations in Panama compete with Teak plantations? An economic estimation

Panama has the highest rate of change in the area of primary forests within Central America. However, to meet growing timber demands, it became popular over the last decades to establish plantations made up of foreign species such as Tectona grandis or Pinus spp. In the majority of the cases the species used are well known; their characteristics such as growth performance have been reviewed intensively and can be accessed in numerous publications. Characteristics of Panama’s native tree species of commercial relevance such as Hieronyma alchorneoides, Swietenia macrophylla and Terminalia amazonia are largely unknown and have been investigated within the study at hand. Using valuation methods of financial mathematics, the competitive position of these three indigenous species was assessed, the results compared to those of T. grandis stands in the same area. Land costs and taxes were not considered, as they would be the same for all species. Financial estimates for indigenous species will enlarge their acceptance for use in reforestation and plantation projects. Using the NPV method and applying the standard scenario, the profitability of T. grandis is lower than that of T. amazonia and S. macrophylla and lies only slightly above the profitability calculated for H. alchorneoides. This result clearly indicates that the investigated native tree species are comparable with T. grandis regarding their economic profitability. Besides its ecological impact, growing native tree species is now also economically legitimate. By calculating land expectation values for all tree species, ideal rotation lengths could be determined. For these species, considerable flexibility exists regarding the optimal rotation length.