Tree plantations on farms: Evaluating growth and potential for success

Interest in native species is growing across the tropics as reforestation of degraded lands becomes more widespread. In this study four tree species native to Panama - Cedrela odorata, Pachira quinata, Samanea saman, and Tabebuia rosea - were grown on rural farms at two dry tropical sites in Panama for up to five years. Survivorship and growth data at these “on-farm” trials are compared to data recorded from nearby experimental or “species selection” trial sites and evaluated in terms of soil fertility and management. Participant farmers were also asked about their interest in planting trees in general as well as their interest in 61 species grown in the species selection trial.Although, on-farm survivorship was variable and generally lower than that found on the species selection trial, one species (S. saman) experienced high and consistent survivorship. High survivorship combined with growth data from farms at both sites for this species suggests it would be a good candidate for extension projects working with rural farmers. Survivorship of other species appears more sensitive to farmer management and/or local site conditions. Generally lower growth on the Los Santos farms as compared to the species-selection trial is attributed to the lower soil fertility (plant available P) at the on-farm sites compared to the species selection trial. In contrast, only one species - P. quinata - had a growth variable found to be significantly lower between the on-farm and species selection trial sites in Rio Hato. C. odorata, P. quinata T. rosea can all be used in on-farm conditions with consideration to specific site and management conditions.By 2009, approximately 80% of the farmers planting trees still wished to participate in tree planting activities. All of the farmers no longer wishing to continue with the project expressed slow growth rates of trees as a principal reason. All but one of these farmers had growth rates for his/her trees markedly below those of the species selection trial nearby. Some farmers wishing to continue had very high mortality rates (>70% for all species), suggesting non-tangible benefits for participating in project activities. Other species that were not tested on-farm but grew well in the species-selection trials and were of interest to local farmers are discussed.As long as specific site and management conditions are carefully considered, data from species selection trials can be useful in informing tree planting projects with rural farmers; however, care should be taken to manage expectations.     

Community composition, species richness, and abundance of birds in field margins of central Mexico: local and landscape-scale effects

Field margin vegetation is among the last vestiges of semi-natural habitat for birds in many agricultural landscapes of tropical regions. However, field margins differ in size, structure, and flora, and their value to birds depends on all these factors and on species-specific habitat preferences. Therefore, we analyzed data on resident and neotropical migratory birds found in 40 field margins of the agricultural landscape of El Bajío, Guanajuato, Mexico. The structural and botanical characteristics of the field margin, and those of the adjacent landscape, were related to bird species richness and abundance. We recorded 61 species of birds of which 36 were migratory. Locally, the size of the field margin (width, height, volume), its vegetative vertical complexity, and the abundance of trees and tree species had a positive effect on bird species richness and abundance. Native trees, especially mesquites, were especially important for many birds observed foraging, nesting, and perching. The most important landscape-scale variables were the density of hedgerows around field margins and the distance to natural vegetation remnants (scrub forest). Bird species richness and abundance were positively affected by the length of the hedgerows within 100 and 200-m-radius circles centered on each field margin. Field margins closer to natural vegetation also had more bird species and individuals. On the basis of our results, we suggest some general management recommendations for improving the habitat for birds in tropical agricultural landscapes.     

Population structure and regeneration of multiple-use tree species in a semi-deciduous African tropical rainforest: Implications for primate conservation

The conservation of threatened frugivorous primates (e.g. chimpanzees) and birds in the Albertine Rift Ecoregion rainforests requires the conservation of food tree species aided by an understanding of their natural regeneration and population trends. However, little is known of the population structure and regeneration patterns of a wide range of multiple-use tree species in many of these forests.     

Microbial properties and litter and soil nutrients after two prescribed fires in developing savannas in an upland Missouri Ozark Forest

On some landscapes periodic fire may be necessary to develop and maintain oak-dominated savannas. We studied the effects of two annual prescribed burns to determine their effect on microbial activity and soil and litter nutrients 1 year after the last burn. Surface litter and soil from the upper 0–5 cm soil layer in three developing savannas (oak-hickory, Quercus-Carya), oak-hickory-pine (Quercus-Carya-Pinus), and pine (Pinus) were collected one year after the second of two annual prescribed burns. Surface litter was analyzed for nutrients and soil was analyzed for phospholipid fatty acids (PLFAs) and nutrients. Surface litter chemistry differed across the three savannas for potassium (K) and boron (B), being significantly (P < 0.05) higher for unburned forest than for burned forest. Among savannas, only sulfur (S) was higher for the pine savanna and B for the oak-hickory savanna, both were higher for unburned forest than for burned forest. For soil, calcium (Ca) and B differed across savannas, being higher for burned forest than for unburned forest. Among savannas, soil pH, Ca, and B concentrations were higher in soil from burned forest than from unburned forest. Total PLFA differed among savannas, but was not affected by burning treatments. However, the amounts of biomarkers for Gram-positive and Gram-negative bacteria were higher while the amount of biomarker for fungal PLFA was lower for burned forest than for unburned forest. Our results indicate that the two annual prescribed burns moderately affected PLFA microbial community structure and litter and soil nutrient concentrations. However, the long-term effects of fire on these study sites are not known and merit further study.     

Three-year growth studies of Leucaena leucocephala (1094) and L. pulverulenta (1001) at two spacings in Texas

The productivity of Leucaena leucocephala and a superior L. pulverulenta family were examined over a 3-year period at spacings (1.5 m×1.5 m and 1.5×3.0 m) chosen to compare two mechanical weeding operations. Leucaena pulverulenta was examined since faster-growing families of this cold-hardy, low-mimosine leucaena species were recently identified. There was no significant difference in yields between the species (P = 0.9060) but there was a significant difference between spacings (P = 0.0491). There was no significant spacing×species, species×year or spacing×year interaction. The annual growth rates for the first, second, and third seasons' growth for L. leucocephala were 3.73, 10.11 and 6.00 t ha⁻¹ at the close spacing and 3.03, 7.14 and 5.04 for the wider spacing. The annual growth-rates for the first, second and third seasons' growth for L. pulverulenta were 2.03, 8.35 and 8.31 t ha⁻¹ at the close spacing and 1.25, 9.38 and 5.29 at the wider spacing. Despite the fact that L. leucocephala froze to the ground in the first and second winter when L. pulverulenta was nearly undamaged, the L. leucocephala coppice resprout was greater than the second year's growth for L. pulverulenta.     

Avian foraging and nesting use of created snags in intensively-managed forests of western Oregon,USA

Snags are critical structural features for managing biological diversity in forests of the Pacific Northwest, USA. However, commercial forests in this region often contain reduced numbers of snags compared to unmanaged forests and managers require effective methods to augment snag numbers in harvest units. Therefore, we created snags by topping live trees with a mechanical harvester and studied foraging and nesting use by cavity-nesting birds of these snags in clearcuts in Douglas-fir (Pseudotsuga mensezii) forests along the west slope of the Cascade Mountain Range and east slope of the Coast Range in Oregon, USA. We used a completely randomized design to assign 6 different treatments (single or scattered distribution by 3 different densities) to 31 different harvest units. We created 1111 snags from February 1997 through April 1999 and monitored them from 2–5 years after harvest (1999–2002). Fraction of created snags with nest cavities in harvest units was generally low across all treatments and years of the study, although some individual stands demonstrated increased nesting use with snag age. While the highest fractions of snags with nest cavities were found in units with low density and scattered snags, the mean fraction of snags used for nesting did not differ among treatments. Treatment type, distribution of snags (i.e., scattered or clumped), and associated interactions did not influence fraction of snags used for foraging. However, fraction of created snags used for foraging in all harvest units increased with snag age. Fraction of snags used for foraging was greatest in the low density treatments. While this technique provides managers with a relatively economical option for creating snags, mechanical harvesters cannot be used to create tall, large snags upon which several cavity-dependent species rely and provides only a partial solution to a critical forest management issue.     

Effects of the commercial extract of aronia on oxidative stress in blood platelets isolated from breast cancer patients after the surgery and various phases of the chemotherapy

Since the extract from berries of Aronia melanocarpa presents antioxidative properties in plasma and in blood platelets, not only from healthy group, but also from patients with benign breast diseases and in patients with invasive breast cancer before surgery, the aim of our present study was to evaluate the oxidative stress by measuring the level of various biomarkers of this process such as the generation of superoxide anion radicals (O(2)(-·)), the amount of carbonyl groups and 3-nitrotyrosine in proteins or the amount of glutathione in blood platelets isolated from breast cancer patients after the surgery and after various phases of the chemotherapy in the presence of A. melanocarpa extract (Aronox) in vitro. We demonstrated in platelet proteins from patients with invasive breast cancer (after the surgery and after various phases of the chemotherapy) higher level of carbonyl groups than in control healthy group. The level of 3-nitrotyrosine in platelet proteins from patients with invasive breast cancer was also significantly higher than in healthy subject group. We observed an increase of other biomarkers of oxidative stress such as O(2)(-·) and a decrease of GSH in platelets from patients with breast cancer (after the surgery and after various phases of the chemotherapy) compared to the healthy group. In model system in vitro our results showed that the commercial extract from berries of A. melanocarpa due to antioxidant action, significantly reduced the oxidative/nitrative stress in platelets from patients with invasive breast cancer caused by the surgery and various phases of the chemotherapy.     

Above- and belowground biomass measurements in an unthinned stand of Sitka spruce (<Emphasis Type="Italic">Picea sitchensis</Emphasis> (Bong) Carr.)

Reporting carbon (C) stocks in tree biomass (above- and belowground) to the United Nations Framework Convention on Climate Change (UNFCCC) should be transparent and verifiable. The development of nationally specific data is considered ‘good practice’ to assist in meeting these reporting requirements. From this study, biomass functions were developed for estimating above- and belowground C stock in a 19-year-old stand of Sitka spruce (Picea sitchensis (Bong) Carr.). Our estimates were then tested against current default values used for reporting in Ireland and literature equations. Ten trees were destructively sampled to develop aboveground and tree component biomass equations. The roots were excavated and a root:shoot (R) ratio developed to estimate belowground biomass. Application of the total aboveground biomass function yielded a C stock estimate for the stand of 74 tonnes C ha⁻¹, with an uncertainty of 7%. The R ratio was determined to be 0.23, with an uncertainty of 10%. The C stock estimate of the belowground biomass component was then calculated to be 17 tonnes C ha⁻¹, with an uncertainty of 12%. The equivalent C stock estimate from the biomass expansion factor (BEF) method, applying Ireland’s currently reported default values for BEF (inclusive of belowground biomass), wood density and C concentration and methods for estimating volume, was found to be 60 tonnes C ha⁻¹, with an uncertainty of 26%. We found that volume tables, currently used for determining merchantable timber volume in Irish forestry conditions, underestimated volume since they did not extend to the yield of the forest under investigation. Mean stock values for belowground biomass compared well with that generated using published models.