Search

Increasing demand for wood is putting pressure on forest resources that are equally under threat from insect pests and diseases. Reported average annual forest loss stands at 0.2% globally, 0.8% in Africa, and 1.6% in Kenya. To meet the increasing demand for forest products in Kenya, the government and private sector have established plantations of non-native tree species dominated by Eucalyptus species, Cupressus lusitanica, and Pinus patula. To ensure successful forest plantation establishment and management schemes, there is a need for sufficient knowledge and understanding of tree growth conditions and threats including pests and diseases. This study aimed at determining the incidence of plantation and tree nurseries in Kimondi Forest, Kenya. Tree plantations were mapped into 2.5 Ha rectangular portion transects parallel to the forest roads. In randomly selected portions, observations were carried out for disease and pest signs and symptoms on various tree parts (leaves, stem, roots, fruits, and twigs). In the tree nurseries, 3 m × 1 m rectangular quadrants were placed on seedling beds and similar observations were made. Collected data indicated a high incidence of nursery seedling pests (5.3 % leaves and 5.1% stems) on Eucalyptus species and least on P. patula (2.4% leaves and 3% stems). Higher incidence of plantation pests (35.0% leaves of Eucalyptus sps.) and least on P. patula stems (1.2%) were recorded. On the other hand, twelve (12.0%) of C. lusitanica and (1.8%) Eucalyptus species plantation twigs were infested by pests. A high incidence of nursery seedling disease (9.8%) was observed on C. lusitanica leaves and least on P. patula stems (3.6%). Higher incidence of plantation diseases (32 %) on leaves of Eucalyptus sps. and least on C. lusitanica stem (1.4%) was recorded. In both tree nurseries and plantations, roots and fruits remained free from pests and disease. Major tree pests and diseases identified in Kimondi forests include (Human, wildlife, livestock, Cinara cupressi, Gonipterus scutellatus, Pinus pini, and Leptocybe invasa) and (damping-off, Fusarium wilt, Botryosphaeria canker, cypress canker, and Mycosphaerella spp.) respectively. These results suggest a need for regular monitoring and intervention measures to control pest and disease infestation in the Kimondi forest.

BackgroundSpecies of the generaEucalyptus,Cupressus, andPinusare the most widely planted tree species in the country in general and in Chilimo dry Afromontane forest in particular. Eucalyptus covers 90% of the total planted forest area in the country. However, only limited information exists in the country regarding aboveground biomass (AGB), belowground biomass (BGB), growth, and yield. This study was conducted to assess the variables on 25 and 30 years of age for three planted species:Cupressus lusitanica,Eucalyptus saligna, andPinus patulain Chilimo plantation forest, in the Central Highlands of Ethiopia. A two-times inventory was conducted in 2012 and 2017. A total of nine square sampled plots of 400 m2each, three plots underCupressus lusitanica, 3Eucalyptus saligna, and 3Pinus patulawere used for data collection. Data on height, diameter, soil, and tree stumps were collected. Percent C, % N, and bulk density was performed following chemical procedure.ResultsThe aboveground biomass ranged from 125.76 to 228.67 t C ha−1and the basal area and number of stems from 3.76 to 25.50 m2 ha−1and 483 to 1175 N ha−1, respectively. The mean annual basal area and volume increment were between 0.97 and 1.20 m2 ha−1 year−1and 10.79 and 16.22 m3 ha−1 year−1. Both carbon and nitrogen stock of the planted forest was non-significant among the tree species.ConclusionThe aboveground biomass, growth, and yield significantly varied among the species.Cupressus lusitanicahad the highest aboveground biomass, volume, and basal area, whileEucalyptus salignahad the lowest value .To a depth of 1 m, total carbon stored ranged from 130.13 to 234.26 t C ha−1. The total annual carbon sequestration potential was 12,575.18 t CO2eq.Eucalyptus has the highest carbon stock density and growth rate than other species.

Plantations of exotic fast‐growing tree species have been widely used for maintaining or restoring ecosystem functions. Despite this, in tropical countries with high biodiversity, these plantations have been the subject of heated debate. We evaluated the long‐term effect of coniferous tree plantations (Cupressus lusitanica, Pinus patula, Pinus elliottii) on the ecological rehabilitation of the Andean highlands in Colombia. To determine degree of rehabilitation, we assessed whether there were differences in the structure or density of native understory vegetation or soil ecological properties between plots established within tree plantations and plots established within other vegetation cover types (secondary forests, ferns, pastures, and abandoned mining areas). Measured variables were combined to create an index of ecological rehabilitation (ERI). We found significant differences in the ERI values among vegetation cover types: secondary forest (11.78) > conifer plantations (P. elliottii: 6.23, P. patula: 5.33, C. lusitanica: 5.24) > ferns (4.16) > pasture (2.50) > abandoned mining areas (0.43). The results obtained showed that, from the structure of native understory vegetation and soil ecological properties, conifer plantations favored the rehabilitation process. However, among them, it was highlighted that the P. elliotii plantations showed significant differences in the density of native understory species, their values being 1.7 and 2.1 times higher than those corresponding to P. patula and C. lusitanica, respectively. Thus, unlike these plantations that could represent an ecological barrier over time, P. elliottii plantations have enabled the advancement of natural succession, showing a high diversity of native species.

The introduction of carbon finance as an incentive in forestry farming has a potential of increasing the amount of carbon sequestered. However, this has created a daunting task among investors in forestry to optimise the joint production of wood and carbon sequestration. For instance, investors might find it profitable to give up some timber returns in exchange for carbon credits. This study evaluated expected income from growing Cupressus lusitanica Mill., Pinus patula Schiede ex Schltdl. & Cham., Eucalyptus saligna Sm. and Juniperus procera Hochst. ex Endl. for wood and/or the carbon market in central Kenya. The global average unit price of carbon and stumpage royalty were used to estimate expected returns from sale of carbon credits and wood, respectively. There were significant differences (p < 0.01) in the expected amount of income from sale of carbon and wood among the four species. Specifically, at economic rotation of 30 years with stand density of 532 trees ha−1 P. patula and C. lusitanica yielded US$28 050 and US$23 650, respectively, from sale of carbon compared with US$59 000 and US$51 000, respectively, from sale of wood. This was twice the value investors receive from clear-felling as compared with sales from carbon. Similarly, at economic rotation of 33 years with stand density of 150 trees ha−1, a forest investor in E. saligna would earn US$15 400 from sale of carbon compared with US$33 000 from sale of wood. Overall, the amount expected to be realised from sale of carbon was lower compared with that from sale of wood. This demonstrates that the price dynamics of carbon offsets in the voluntary and the compliance markets need to remain competitive and attractive for the forest owners to give up some timber returns in exchange for carbon income or to modify forest management regulation in order to increase carbon sequestration.Keywords: carbon credits, carbon sequestration, Cupressus lusitanica, Eucalyptus saligna, Juniperus procera, Pinus patula, sale of wood

Climate change caused by global warming, is a phenomenon partly resulting from abundance of carbon dioxide in the atmosphere. Carbon sequestration through forestry plantations has a potential in ameliorating global environmental problems such as atmospheric accumulation of carbon dioxide and related climate change. The aim of this study was to estimate carbon sequestered by commonly grown plantation species across different ages. Four tree species were selected for the present study. Total 36 sample plots were selected for estimation of selected tree plantation biomass. Biomass data was collected at different age intervals (5-10 years, 11-15 years and ≥ 16 years) of tree plantation species. At each age interval of tree plantation three sample plots were selected for each species. A plot of 20 m × 20 m was established randomly in all study sites. Diameter at breast height (DBH) of each tree (≥ 10 cm) within 20 m × 20 m sample plot was measured by using caliper and height of each tree was measured by using hypsometer. The litter samples where be collected from the four corners and at the center with sub-sample of 1 m × 1 m in each sample plot. Soils were sampled in the same sub sample plots as litter. Aboveground and belowground biomass was estimated using specific species allometric equation. Aboveground carbon of Eucalyptus saligna, Cupressus lusitanica, Grevillea robusta and Pinus patula were sequestered (38.74, 39.05, 23.49 and 7.27 t/ha) respectively. Below ground carbon content of Eucalyptus saligna, Cupressus lusitanica, Grevillea robusta and Pinus patula (10.07, 10.15, 6.11 and 1.89 t/ ha) respectively. According to this study Eucalyptus saligna (0.006 t/ha), Cupressus lusitanica (0.007 t/ha), Pinus patula (0.006 t/ha) and Grevillea robusta (0.006 t/ha) were sequestered comparable litter carbon content. The study showed that Eucalyptus saligna (10.85 t/ha), Cupressus lusitanica (10.87 t/ha), Pinus patula (10.67 t/ha) and Grevillea robusta (11.36 t/ha) were storage similar soil organic carbon. According to this study the total carbon content of Grevillea robusta was 40.98, Eucalyptus saligna 59.68, Pinus patula 19.83 and Cupressus lusitanica 60.08 t/ha. Eucalyptus saligna and Cupressus lusitanica were sequestered high carbon, followed by Grevillea robusta and Pinus patula respectively.

Background and aims Exotic coniferous species have been used widely in restoration efforts in tropical montane forests due to their tolerance to adverse conditions and rapid growth, with little consideration given to the potentialecologicalbenefits provided by native treespecies.The aim of this study was to elucidate differences in litterfall and nutrient flow between a montane oak forest (Quercus humboldtii Bonpl.) and exotic coniferous plantations of pine (Pinus patula Schltdl. & Cham.) and cypress (Cupressus lusitanica Mill.) in the Colombian Andes. Methods Litter production, litter decomposition rate, and element composition of leaf litter were monitored during 3 years. Results Litter production in the oak forest and pine plantation was similar, but considerably lower in the cypress plantation . Similar patterns were observed for nutrient concentrations in litterfall, with the exception of Ca which was three times higher in the cypress plantation. The annual decay rate of litter was faster in the montane oak forest than in either of the exotic coniferous plantations. The potential and net return of nutrients

La caída y descomposición de hojarasca representan los principales ingresos de materia orgánica y nutrientes a los ecosistemas forestales. Se estudiaron la caída y acumulación de hojarasca fina y el retorno de nutrientes, en un robledal (Quercus humboldtii) y en plantaciones de pino (Pinus patula) y ciprés (Cupressus lusitanica) en tierras altas de Colombia. La caída de hojarasca fina fue similar entre el robledal (7.5Mg/ha.a) y el pinar (7.8Mg/ha.a), y muy inferior en el cipresal (3.5Mg/ha.a). El mantillo representó 1.76, 1.73 y 1.3Mg/ha.a en el robledal, pinar y cipresal, respectivamente. El tiempo medio de residencia (TMR) del mantillo siguió la secuencia: cipresal (3.3 años)>pinar (2.1 años)>robledal (1.8 años). La cantidad de nutrientes retenidos en el mantillo siguió la secuencia: pinar (115kg/ ha)>robledal (78kg/ha)>cipresal (24kg/ha). Los menores TMR de nutrientes se presentaron para la hojarasca foliar del robledal, en su mayoría inferiores a 1.0 años. En términos de la función ecosistémica en el robledal los procesos estudiados son muy superiores vía provisión de nutrientes al suelo y regulación de los ciclos biogeoquímicos, aspectos que deben ser considerados previa implementación de programas de repoblamiento forestal.Biogeochemical cycles in natural forest and conifer plantations in the high mountains of Colombia. Plant litter production and decomposition are two important processes in forest ecosystems, since they provide the main organic matter input to soil and regulate nutrient cycling. With the aim to study these processes, litterfall, standing litter and nutrient return were studied for three years in an oak forest (Quercus humboldtii), pine (Pinus patula) and cypress (Cupressus lusitanica) plantations, located in highlands of the Central Cordillera of Colombia. Evaluation methods included: fine litter collection at fortnightly intervals using litter traps; the litter layer samples at the end of each sampling year and chemical analyses of both litterfall and standing litter. Fine litter fall observed was similar in oak forest (7.5Mg ha/y) and in pine (7.8Mg ha/y), but very low in cypress (3.5Mg ha/y). Litter standing was 1.76, 1.73 and 1.3Mg ha/y in oak, pine and cypress, respectively. The mean residence time of the standing litter was of 3.3 years for cypress, 2.1 years for pine and 1.8 years for oak forests. In contrast, the total amount of retained elements (N, P, S, Ca, Mg, K, Cu, Fe, Mn and Zn) in the standing litter was higher in pine (115kg/ha), followed by oak (78kg/ha) and cypress (24kg/ha). Oak forests showed the lowest mean residence time of nutrients and the highest nutrients return to the soil as a consequence of a faster decomposition. Thus, a higher nutrient supply to soils from oaks than from tree plantations, seems to be an ecological advantage for recovering and maintaining the main ecosystem functioning features, which needs to be taken into account in restoration programs in this highly degraded Andean mountains. Rev. Biol. Trop. 59 (4): 1883-1894. Epub 2011 December 01.

Lack of empirical data on the effects of the taungya system on establishment and early growth of softwood plantations have partly contributed to controversial decisions regarding the continued suitability of the system for plantation establishment in Kenya. This study examined effectiveness of taungya systems of forest plantation establishment using Cupressus lusitanica and Pinus patula trees with Zea mays (maize) as a test intercrop on two contrasting site types (deep and shallow soils) in Mt. Elgon forest, western Kenya . Four treatments were evaluated in each site: trees with or without weed control, trees intercropped with maize, and sole maize. Results showed that tree survival, growth and nutrient uptake, and maize growth and yield were higher in the deep soil site than the shallow site. The taungya system improved tree survival and growth, effects being greater in the deep than the shallow soil site. Both Cupressus lusitanica and Pinus patula trees had the same effects on maize growth and yield, reducing maize growth by 41–48% in the deep soil sites, and by 16–26% in the shallow site. Vector nutrient analysis and vector competition analysis of the treatment effects on growth and nutrient uptake of the trees and the maize crop suggested competition for N on the deep soils, but competition for K and P on the shallow soils. The study has demonstrated the applicability of graphical vector competition analysis in diagnosing tree–crop interactions in agroforestry.

Models are important research tools for predicting the build-up of soil organic carbon (SOC), because they provide an increased insight into factors that are involved in the build-up process. The CO2Fix (v. 3.1) model was used to examine the influence of litter production, litter quality and microclimate on differences in SOC accretion under exotic tree species established on farmland in southwestern Ethiopia. The SOC storage under Cupressus lusitanica was larger than that under the other two investigated species ( Pinus patula and Eucalyptus grandis ). This was mainly because of the higher total litter input and higher proportion of fine woody litter (branches and coarse roots) in the Cupressus stand. SOC accretion was greater under Pinus than under Eucalyptus . However, the total litter input in the Pinus and Eucalyptus stands was nearly the same. The difference between the Pinus and Eucalyptus stands was best explained by the fact that Pinus produced more fine woody litter than did Eucalyptus . Litter quality and microclimate only accounted for a minor part of the differences in SOC storage in the Cupressus , Pinus and Eucalyptus stands. Therefore, the results suggested that total litter input and the proportion of fine woody litter were the main factors that accounted for the inter-specific differences in SOC accretion.

At Belete forest in southwestern Ethiopia (7°33′N, 36°35′E), tree plantations were established on abandoned farmland, which was previously mainly used for maize cultivation. Total carbon and 13 C analyses were used to evaluate the changes in soil organic carbon (SOC) pools associated with land use changes using a comparative approach. Forest clearing followed by continuous cultivation of crops caused a loss of 43% (75.4 Mg ha − 1 ) total SOC and 73% (128.4 Mg ha − 1 ) forest derived SOC after nearly 75 years. The net loss of SOC was lower because of addition of 53.0 Mg ha − 1 of SOC of C 4 crop origin (mainly maize) to the farmland. On the other hand, afforestation of farmland led to a net accretion of SOC of 69.6 and 29.3 Mg ha − 1 after 20 years under Cupressus lusitanica and Pinus patula stands, respectively . The SOC accretion of plantation origin amounted to 63.3 Mg ha − 1 under C. lusitanica and 24.2 Mg ha − 1 under P. patula. Contrary to the results obtained in some other studies, the SOC of C 4 origin did not decline in these stands. This could be attributed to pasture grasses of C 4 origin that took over after land abandonment and continued to grow under the tree canopies. The grasses could thus have compensated for the SOC loss. SOC might also have been close to a steady state under the pre-plantation period. Based on the SOC amount found in a reference stand of native forest, afforestation with Eucalyptus grandis during 20 years, preceded by 20 years of cultivation and 35 years of pasture, returned the total SOC to nearly pre-deforestation levels. SOC accumulation rates of 1–3.2 Mg ha − 1 y − 1 are apparently possible 20 years after afforestation of an abandoned farmland but the accumulation rate is species dependent.

This study was undertaken to evaluate the effect of tree species on soil properties. Soil δ15N, total N, C:N ratio, base cations and available P were analyzed under farmland, native forest and tree plantations established on abandoned farmland at Belete forest. Changes associated with land use were evaluated using a comparative approach. Forest clearing followed by continuous cultivation of annual crops resulted in a significant decline in total N, base cations and available P within 0–10 or 0–20 cm depth. Assuming a linear rate of loss, total N declined by 90.6 kg ha−1 year−1 or by 38% (6.8 Mg ha−1) of the level in native forest during the 75 years of cultivation. The 15N enrichment of soil and litter N in the farmland may indicate losses of N through leaching and harvest. The degree of change in soil properties under exotic trees after 20 years of afforestation of former farmland depended on tree species. Total N within 0–50 cm depth increased by 5.7 Mg ha−1 under Cupressus lusitanica and 2.0 Mg ha−1 under Pinus patula. The decrease in δ15N value with afforestation was greater for C. lusitanica than for P. patula, indicating that N cycling under C. lusitanica progressed more towards ‘native forest like’ conditions. Under C. lusitanica, exchangeable Ca2+ increased significantly at 0–5 cm. Exchangeable K+ increased significantly within 0–30 cm depth under both C. lusitanica and P. patula. The increased C:N ratio under these tree species was attributed to recent organic matter (OM) addition. The soil under Eucalyptus grandis, established on former mixed land use (pasture plus farmland), had nearly similar δ15N, TN, exchangeable Ca2+ and K+ to native forest. The residual effect of 15N-depleted C4 pasture grasses might explain the lack of difference in soil δ15N profile below 10 cm depth between E. grandis and native forest. Greater OM inputs by E. grandis probably account for the greater C:N ratio relative to native forest soil.

To assess the effects of canopy characteristics and associated understory environmental factors of tree plantations on native woody species colonization, we measured canopy closure percent (CCP), leaf area index (LAI), understory air and soil temperatures as well as soil moisture in two broadleaved and two coniferous plantations in southern Ethiopia. The plantation species were Cordia africana (indigenous and broadleaved), Eucalyptus saligna (exotic and broadleaved), Cupressus lusitanica (exotic and coniferous) and Pinus patula (exotic and coniferous). The broadleaved species had significantly lower CCP (P

Hemispherical photographs and a quantum sensor were used to study the canopy photosynthetic photon flux density (PPFD) transmittance of five forest plantation species in Ethiopia. Red/far-red (R/FR) ratios and temperatures beneath the forest plantations were also measured. The species studied were: Eucalyptus globulus , Pinus patula , Cupressus lusitanica , Grevillea robusta , and Juniperus procera . The canopies of E. globulus , P. patula and G. robusta transmitted about three times as much PPFD as J. procera or C. lusitanica plantations. Furthermore, plantations of G. robusta and E. globulus had the highest, while J. procera had the lowest R/FR ratio. In contrast to J. procera and C. lusitanica , E. globulus and G. robusta had relatively open crowns, higher crown-bases and lower leaf area indices, and as a result, their canopies had higher PPFD transmittance percentages as well as higher below-canopy R/FR ratios and temperatures. From the perspective of understory light regime, plantations of E. globulus and G. robusta are best suited for promoting the natural regeneration of native species. In general, opening of gaps in plantations of heavy-shading tree species may increase the herbaceous layer ground cover, enhance the colonisation and growth of native woody species and consequently may also increase the floristic diversity of mono-specific plantations.

Species richness and diversity and soil physical and chemical properties were compared between a mature lower montane rain forest (LMRF) and abandoned 21-year-old plantations of introduced Pinus patula and Cupressus lusitanica in the central Andes of Colombia (2000m). In 0.1ha plots, species richness (number of species) and diversity (Shannon and Simpson indexes) were higher in the LMRF, followed by P. patula and C. lusitanica plantations. There were 56species and 30families of higher plants in the LMRF, 26species and 15families in the P. patula plantation, and 18species and 10families in the C. lusitanica plantation. There were no statistically significant differences (p

Hemos estudiado durante tres años variables relacionadas con nutrientes, tales como la retranslocación, la eficiencia en su uso y la caída de hojarasca fina en un bosque de roble Quercus humboldtii Bonpl. y en plantaciones forestales de pino pátula (Pinus patula) y ciprés (Cupressus lusitanica) de Antioquia, Colombia. Las cantidades de hojarasca foliar regresadas hasta el suelo siguieron la secuencia decreciente roble (5313.3 kg ha-1 año-1) > pino (4866.5 kg ha-1 año-1) > ciprés (2460.3 kg ha-1 año-1). Las especies de coníferas mostraron la mayor eficiencia en el uso de nutrientes para la mayoría de nutrientes estudiados, con excepción del P, el cual alcanzó el máximo absoluto en el bosque de roble, donde además se registró una clara retranslocación de este nutriente, probablemente como resultado de su escasa disponibilidad en estos suelos derivados de cenizas volcánicas. La retranslocación permite la conservación del nutriente reduciendo sus pérdidas por lavado foliar y desde la hojarasca desprendida del dosel. De hecho, encontramos ganancias de P vía deposición neta -la cual incluye lavado foliar y deposición atmosférica-, lo que indica que la especie absorbe el P contenido en el agua lluvia desde las hojas antes de que alcance el piso del bosque. La baja eficiencia en el uso de N se debe probablemente a su escasa disponibilidad edáfica, dadas sus bajas tasas de mineralización en estos bosques montanos. El K mostró la máxima retranslocación, con valores influenciados por su carácter eminentemente móvil, de acuerdo con los máximos absolutos encontrados para él en la deposición neta. Con excepción del Mg, no se presentó una clara relación entre la retranslocación y la eficiencia en el uso de nutrientes (EUN). We have studied nutrient related variables such as reallocation, nutrient use efficiency (NUE) and fine litter fall for three years in an oak forest Quercus humboldtii Bonpl. and also in some other forest plantations like pine, Pinus patula, and cypress, Cupressus lusitanica, in Antioquia, Colombia. Leaf litter quantities returned to the soil followed a falling sequence: oak (5313.3 kg ha-1 year-1) > pine (4866.5 kg ha-1 year-1) > cypress (2460.3 kg ha-1 year-1). The coniferous species showed the highest NUE for the majority of elements that were examined, except for P, which reached its absolute maximum in the oak forest -where a clear reallocation of this nutrient was also recorded-, probably because of its reduced availability in these volcanic ash-derived soils. Nutrient reallocation allows the conservation of the nutrients by reducing its loss from leaching and litter-fall, thereby closing the nutrient cycle in this native forest. In fact, P gains from net deposition were found there -this includes foliar leaching and atmospheric deposition-, which indicates that the species absorbs the P contained in rainfall from the leaves before it reaches the forest ground. N's low-efficiency use was probably due to its low availability in soil, given its low mineralization rates in these montane forests. K showed the highest reallocation values. Such figures are influenced by its clearly mobile character, according to the highest net deposition levels also verified for this element. With the exception of Mg, there was no clear relationship between the reallocation process and NUE. Estivemos estudando durante três anos variáveis relacionadas com nutrientes, tais como a retranslocação, a eficiencia no uso e na caída de folhas finas num bosque de roble Quercus humboldtii Bonpl. E nas plantações florestais de pinos pátulas (Pinus patula) e cipreste (Cupressus lusitanica) de Antióquia, Colômbia. As quantidades de folhas caídas no solo seguiram a seqüência decrescente roble (5313.3 kg ha-1 año-1) > pinos (4866.5 kg ha-1 año-1) > cipreste (2460.3 kg ha-1 año-1). As espécies de coníferas mostraram a maior eficiência no uso de nutrientes em relação à maioria dos nutrientes estudados, com exceção do P, o qual alcançou o máximo absoluto no bosque roble, aonde, ademais se registrou uma clara retranslocação deste nutriente,provavelmente como resultado da sua escassa disponibilidade nestes solos derivados das cinzas vulcânicas. A retranslocação permite a conservação do nutriente reduzindo as suas perdas pelo lavado foliar e desde a folhagem caída do dosel.De fato encontramos ganancias de P via deposição neta - a qual inclui lavado foliar e deposição atmosférica -, o que indica que a espécie P absorve o conteúdo da água das chuvas desde as folhas antes de que alcancem o chão do bosque.A baixa eficiência no uso de N se deve provavelmente a sua escassa disponibilidade edáfica, dadas suas baixas taxas de mineralização neste bosques montanhosos. O K mostrou a máxima retranslocaçao, com valores influenciados pelo seu alto caráter movel, de acordo com os máximos absolutos encontrados na deposição neta. Com exceção do Mg, não se apresentou uma clara relação entre a retranslocação e a eficiência no uso de nutrientes (EUN).

Data from Cupressus lusitanica and Pinus patula were used to develop total and exponential form merchantable volume models, and implicit taper functions. The exponential form merchantable volume model to a specified top diameter limit showed marked improvement compared with the unbounded non exponential form merchantable volume model of Burkhart (1977). Implicit taper functions derived from the exponential form merchantable volume models were found superior to taper functions obtained from the non exponential merchantable volume models. In general, these models are essential management tools for the plantation of the species and in particular provide stock volume estimates by end use type. Key words: C. lusitanica , Merchantable volume models, Taper functions, Total tree volume models, P. patula.

22 p., [ESP] Hemos estudiado durante tres años variables relacionadas con nutrientes, tales como la retranslocación, la eficiencia en su uso y la caída de hojarasca fina en un bosque de roble Quercus humboldtii Bonpl. y en plantaciones forestales de pino pátula (Pinus patula) y ciprés (Cupressus lusitanica) de Antioquia, Colombia. Las cantidades de hojarasca foliar regresadas hasta el suelo siguieron la secuencia decreciente roble (5313.3 kg ha-1 año-1) > pino (4866.5 kg ha-1 año-1) > ciprés (2460.3 kg ha-1 año- 1). Las especies de coníferas mostraron la mayor eficiencia en el uso de nutrientes para la mayoría de nutrientes estudiados, con excepción del P, el cual alcanzó el máximo absoluto en el bosque de roble, donde además se registró una clara retranslocación de este nutriente, probablemente como resultado de su escasa disponibilidad en estos suelos derivados de cenizas volcánicas. La retranslocación permite la conservación del nutriente reduciendo sus pérdidas por lavado foliar y desde la hojarasca desprendida del dosel. De hecho, encontramos ganancias de P vía deposición neta –la cual incluye lavado foliar y deposición atmosférica–, lo que indica que la especie absorbe el P contenido en el agua lluvia desde las hojas antes de que alcance el piso del bosque. La baja eficiencia en el uso de N se debe probablemente a su escasa disponibilidad edáfica, dadas sus bajas tasas de mineralización en estos bosques montanos. El K mostró la máxima retranslocación, con valores influenciados por su carácter eminentemente móvil, de acuerdo con los máximos absolutos encontrados para él en la deposición neta. Con excepción del Mg, no se presentó una clara relación entre la retranslocación y la eficiencia en el uso de nutrientes (eun)., [ENG] We have studied nutrient related variables such as reallocation, nutrient use efficiency (nue) and fine litter fall for three years in an oak forest Quercus humboldtii Bonpl. and also in some other forest plantations like pine, Pinus patula, and cypress, Cupressus lusitanica, in Antioquia, Colombia. Leaf litter quantities returned to the soil followed a falling sequence: oak (5313.3 kg ha-1 year-1) > pine (4866.5 kg ha-1 year-1) > cypress (2460.3 kg ha-1 year-1). The coniferous species showed the highest nue for the majority of elements that were examined, except for P, which reached its absolute maximum in the oak forest –where a clear reallocation of this nutrient was also recorded–, probably because of its reduced availability in these volcanic ash-derived soils. Nutrient reallocation allows the conservation of the nutrients by reducing its loss from leaching and litter-fall, thereby closing the nutrient cycle in this native forest. In fact, P gains from net deposition were found there –this includes foliar leaching and atmospheric deposition–, which indicates that the species absorbs the P contained in rainfall from the leaves before it reaches the forest ground. N’s low-efficiency use was probably due to its low availability in soil, given its low mineralization rates in these montane forests. K showed the highest reallocation values. Such figures are influenced by its clearly mobile character, according to the highest net deposition levels also verified for this element. With the exception of Mg, there was no clear relationship between the reallocation process and nue., Al Área de Biogeoquímica del Laboratorio de Ecología César Pérez Figueroa y a la Estación Forestal de Piedras Blancas de la Universidad Nacional de Colombia, Sede Medellín, por su apoyo técnico y financiero, y al personal que allí trabaja, en particular a José Vicente Betancur por su valioso concurso en el ascenso a los árboles para la toma de muestras y a Gloria Mazo por los oportunos procesamientos y determinaciones químicas en laboratorio. Agradecemos asimismo el soporte técnico y financiero prestado por el Laboratorio de Suelos del Área de Edafología y Química Agrícola de la Universidad de Salamanca, España, y a Empresas Públicas de Medellín por el acceso a los predios donde se realizó el estudio y por el suministro de información meteorológica. El trabajo fue además financiado por la Dirección de Investigaciones de la Universidad Nacional de Colombia (dime). Los autores agradecemos especialmente a los ingenieros forestales Jorge Andrés Ramírez y Claudia Marcela Zapata, quienes participaron en el establecimiento y monitoreo del ensayo.

This study was done to determine the extent of tree damage (primarily bark‐stripping) caused by blue monkeys (Cerco‐pithecus mitis) in the Sokoine University of Agriculture Training Forest in the Mount Meru Forest Plantations. The impact of monkeys was extensive; 88.7% of the pine (Pinus patula) amd 79.5% of the cypress (Cupressus lusitanica) trees were damaged. Intermediate pine trees were damaged more than dominant trees, whereas dominant cypress trees incurred the most damage. Suppressed trees of both species were least damaged. For all types of trees the most severe damage occurred at the middle and top.of the tree trunks. Damage was low in the rain season and increased in the dry season, peaking in June and July when 22% of the trees were damaged. Differences in the ease of bark peeling and nutritional elements in the bark of the two species, and shortages of natural foods, are discussed as possible explanations for the variations in damage between seasons, tree species and types of trees.

12 páginas, 3 figuras, 4 tablas, 46 referencias.-- cmartin@irnase.csic.es, Substrate quality and decomposition (measured as CO2 release in laboratory microcosms) of fresh leaf litter and fine roots of Cupressus lusitanica, Pinus patula, Eucalyptus grandis and native forest trees were studied. Changes in litter chemistry in each forest stand were analysed by comparing fresh leaf litter (collected from trees) and decomposed litter from the forest floor. Elemental concentrations, proximate fractions including monomeric sugars, and cross polarisation magic-angle spinning (CPMAS) 13C NMR spectra were analysed in leaf litters, decomposed litter and fine roots. Leaf litters and fine roots varied in their initial substrate chemistry with Ca concentration in leaf litters being higher than that in fine roots. In each stand, fine roots had a higher acid unhydrolysable residue (AUR) (except for the Pinus stand), higher holocellulose concentration and lower concentration of water-soluble extractives (WSE) and dichloromethane extractives (NPE) than fresh leaf litter. Likewise, 13C NMR spectra of fine roots showed lower alkyl and carboxyl C, and higher phenolic (except P. patula), aromatic and O-alkyl C proportions than leaf litters. Compared with fresh leaf litter, decomposed litter had lower concentrations of potassium, holocellulose, WSE, NPE, arabinose and galactose, similar or higher concentrations of Mg, Ca, S and P, and higher concentrations of N and AUR. CPMAS 13C NMR spectra of decomposed litter showed a higher relative increase in signal intensity due to methoxyl C, aromatic C, phenolic C and carboxylic C compared with alkyl C. In a microcosm decomposition study, the proportion of initial C remaining in leaf litter and fine roots significantly fitted an exponential regression model. The decomposition constants (k) ranged between 0.0013 and 0.0030 d−1 for leaf litters and 0.0010–0.0017 d−1 for fine roots. In leaf litters there was a positive correlation between the k value and the initial Ca concentration, and in fine roots there was an analogous positive correlation with initial WSE. Leaf litters decomposed in the order Cupressus>native forest>Eucalyptus∼Pinus, and fine roots in the order Pinus>native forest>Cupressus∼Eucalyptus. In each stand the fine root decomposition was significantly lower than the leaf litter decomposition, except for the P. patula stand where the order was reversed., This study was supported by the Swedish International Development Agency and Wondo Genet College of Forestry.

El agua gravitacional y su composición química fueron medidos en bosques montanos de Quercus humboldtii y reforestados (Pinus patula y Cupressus lusitanica) de la región de Piedras Blancas, Antioquia (Colombia), por un período de tiempo de dos años. Se utilizaron lisímetros sin tensión con el fin de estimar el agua gravitacional y los flujos de nutrientes a diferentes profundidades en el perfil del suelo. El mayor valor anual de agua gravitacional en el nivel más profundo (50- 80 cm), fue hallado en la cobertura de ciprés ( 492,7 mm), seguido por pino pátula ( 14,2 mm) y roble ( 2,0 mm). De manera similar ocurrió con la pérdida de nutrientes, mostrando el mismo patrón hallado para el agua gravitacional. Así, para roble, pátula y ciprés, en su orden, se presentaron los siguientes valores de pérdida: Ca: 0,004, 0,084 y 2,270 kg ha-1 año-1; P: 0,008, 0,052 y 1,234 kg ha-1 año-1; Mg: 0,004, 0,022 y 0,667 kg ha-1 año-1. De K se registraron 0,08 y 7,092 kg ha-1 año-1 para roble y ciprés respectivamente. Estos flujos siguieron el siguiente orden según cobertura, roble: K>P>Ca>Mg, pátula: Ca>Fe>P>Mg>Zn>Mn, y ciprés: K>Mn>Ca>P>Fe>Zn>Mg. Gravitational flow and its chemical composition were measured in montane oak forests (Quercus humboldtii), in pine (Pinus patula) and cypress (Cupressus lusitanica) plantations in Piedras Blancas, Antioquia ( Colombia ), over two years. Zero tension lysimeters were used at different depth soil levels. The highest gravitational flow value at highest depth (50- 80 cm) was obtained in cypress plot ( 492,7 mm), followed by pine ( 14,2 mm) and oak forest ( 2,0 mm). A similar behavior was encountered for nutrient losses, following the same pattern as gravitational flow. Thus, for oak, pine and cypress, nutrient losses were respectively: Ca: 0,004, 0,084 and 2,270 kg ha-1 y-1; P: 0,008, 0,052 and 1,234 kg ha-1 y -1; Mg: 0,004, 0,022 and 0,667 kg ha-1 y-1. K losses were 0,08 and 7,092 kg ha-1 y-1 for oak forest and cypress plantation respectively. Nutrient losses followed the next order for each type of forest: oak: K>P>Ca>Mg, pine: Ca>Fe>P>Mg>Zn>Mn, and cypress: K>Mn>Ca>P>Fe>Zn>Mg.

En bosques montanos naturales de Quercus humboldtii y reforestados (Pinus patula y Cupressus lusitanica) de la región de Piedras Blancas, Antioquia (Colombia), fue evaluada la producción de hojarasca por un periodo de 2 años. Se utilizaron trampas de hojarasca con el fin de recoger el material desprendido del dosel para su posterior separación en fracciones y pesado respectivo. El promedio de caída de hojarasca anual para Q. humboldtii, P. patula y C. lusitanica fue de 7877,20; 8362,47 y 3725,97 kg ha-1año-1 respectivamente; siendo la fracción foliar la que mayor participación tuvo en la producción total. Mediante análisis de regresión lineal múltiple se ajustaron modelos de producción de hojarasca según fracciones por cobertura en función de diferentes variables hidrológicas, tales como la intensidad y la cantidad de lluvia del período simultáneo a la recolección de la hojarasca o inmediatamente anterior. Litter production was measured over two years in a montane oak forest (Quercus humboldtii) and in pine (Pinus patula) and cypress (Cupressus lusitanica) plantations in Piedras Blancas, Antioquia ( Colombia ). Litter traps were used in order to collect litterfall to be subsequently separated into fractions and weighed. Annual mean litterfall for Q. humboldtii, P. patula and C. lusitanica was of 7877,20; 8362,47 and 3725,97 kg ha-1year-1 respectively; being the leaf fraction of highest participation in total production. Multiple linear regression models were used to fit litter production for each fraction and forest cover as a function of different hydrological variables such as intensity and quantity of precipitation, both during the period when the leaf litter was collected and immediately preceding one.

En un bosque montano natural de roble (Quercus humboldtii Bonpl.) y en plantaciones forestales de pino pátula (Pinus patula Schltdl. y Cham.) y de ciprés (Cupressus lusitanica Mill.) de Piedras Blancas, Antioquia, Colombia, fueron medidos durante dos años los flujos de nutrientes a través de la hojarasca. En cada ecosistema se emplearon 20 trampas de hojarasca (0,5m² cada una) con el fin de recoger el material desprendido del dosel para su posterior separación en fracciones y análisis químico. Las cantidades de hojarasca fina siguieron el orden: pino pátula (8362,47kg·ha-1·año-1), roble (7877,20kg·ha-1·año-1) y ciprés (3725,97kg·ha-1·año-1). Las cantidades de nutrientes que retornaron a través de la hojarasca foliar de la especie dominante en cada bosque fueron C>N>Ca>K>Mg>S>P en bosque de roble, C>N>P>Ca>Mg>K>S en plantación de pino pátula, y C>Ca>N>K>S>Mg>P en plantación de ciprés. Los resultados muestran un menor retorno de elementos hasta el piso del bosque en las plantaciones de coníferas y un retorno real posiblemente más lento como producto de los mayores valores de la relación C/N del material foliar de las especies de coníferas. In a natural montane oak forest (Quercus humboldtii Bonpl.) and in pine (Pinus patula Schltdl. y Cham.) and cypress (Cupressus lusitanica Mill.) plantations in Piedras Blancas, Antioquia, Colombia, nutrient litterflow was measured over two years. On each ecosystem twenty litter traps (0.5m² each one) were used to collect litterfall to be subsequently separated into fractions and chemically analyzed. Fine litterfall quantities followed the order pine plantation (8362.47kg·ha-1·year-1), oak forest (7877.20kg·ha-1·year-1) and cypress plantation (3725.97kg·ha-1·year-1). Nutrients returning to the forest floor through leaf litter of the dominant species on each forest were C>N>Ca>K>Mg>S>P in oak forest, C>N>P>Ca>Mg>K>S in pine plantation, and C>Ca>N>K>S>Mg>P in cypress plantation. Results show a lower nutrients return reaching forest floor in pine and cypress plantations, and probably a slower real nutrient return as the result of higher C/N ratio values from leaf litter from coniferous species. Em um bosque montano natural de carvalho-roble (Quercus humboldtii Bonpl.) e em plantações florestais de pinus pátula (Pinus patula Schltdl. e Cham.) e de cipreste (Cupressus lusitanica Mill.) de Piedras Blancas, Antioquia, Colombia, foram medidos durante dois anos os fluxos de nutrientes a través da serapilheira. Em cada ecossistema foram empregadas 20 armadilhas de serapilheira (0,5m² cada uma) com o fim de recolher o material desprendido do dossel para sua posterior separação em frações e análise química. As quantidades de serapilheira fina seguiram a seguinte seqüência: pinus pátula (8362,47kg·ha-1·ano-1), carvalho-roble (7877,20kg·ha-1·ano-1) e cipreste (3725,97kg·ha-1·ano-1). As quantidades de nutrientes que retornaram através da serapilheira foliar da espécie dominante em cada bosque foram C>N>Ca>K>Mg>S>P em bosque de carvalho-roble, C>N>P>Ca>Mg>K>S em plantação de pinus pátula, e C>Ca>N>K>S>Mg>P em plantação de cipreste. Os resultados mostram um menor retorno de elementos até o piso do bosque nas plantações de coníferas e um retorno real possivelmente mais lento como produto dos maiores valores da relação C/N do material foliar das espécies de coníferas.

En bosques montanos naturales de Quercus humboldtii y reforestados (Pinus patula y Cupressus lusitanica) de la región de Piedras Blancas, Antioquia (Colombia), fue evaluada la producción de hojarasca por un periodo de 2 años. Se utilizaron trampas de hojarasca con el fin de recoger el material desprendido del dosel para su posterior separación en fracciones y pesado respectivo. El promedio de caída de hojarasca anual para Q. humboldtii, P. patula y C. lusitanica fue de 7877,20; 8362,47 y 3725,97 kg ha-1año-1 respectivamente; siendo la fracción foliar la que mayor participación tuvo en la producción total. Mediante análisis de regresión lineal múltiple se ajustaron modelos de producción de hojarasca según fracciones por cobertura en función de diferentes variables hidrológicas, tales como la intensidad y la cantidad de lluvia del período simultáneo a la recolección de la hojarasca o inmediatamente anterior.

El agua gravitacional y su composición química fueron medidos en bosques montanos de Quercus humboldtii y reforestados (Pinus patula y Cupressus lusitanica) de la región de Piedras Blancas, Antioquia (Colombia), por un período de tiempo de dos años. Se utilizaron lisímetros sin tensión con el fin de estimar el agua gravitacional y los flujos de nutrientes a diferentes profundidades en el perfil del suelo. El mayor valor anual de agua gravitacional en el nivel más profundo (50-80 cm), fue hallado en la cobertura de ciprés (492,7 mm), seguido por pino pátula (14,2 mm) y roble (2,0 mm). De manera similar ocurrió con la pérdida de nutrientes, mostrando el mismo patrón hallado para el agua gravitacional. Así, para roble, pátula y ciprés, en su orden, se presentaron los siguientes valores de pérdida: Ca: 0,004, 0,084 y 2,270 kg ha-1 año-1, P: 0,008, 0,052 y 1,234 kg ha-1 año-1, Mg: 0,004, 0,022 y 0,667 kg ha-1 año-1. De K se registraron 0,08 y 7,092 kg ha-1 año-1 para roble y ciprés respectivamente. Estos flujos siguieron el siguiente orden según cobertura, roble: Kmayor quePmayor queCamayor queMg, pátula: Camayor queFemayor quePmayor queMgmayor queZnmayor queMn, y ciprés: Kmayor queMnmayor queCamayor quePmayor queFemayor queZnmayor queMg. Agroforestería-Agroforestales

En la región de Piedras Blancas, Antioquia - Colombia, se realizó un muestreo de raíces finas (£ 5 mm) en tres parcelas permanentes establecidas en bosques de pino pátula (Pinus patula Schltdl y Cham), ciprés (Cupressus lusitanica Mill) y roble (Quercus humboldtii Bonpl.) a diferentes profundidades: 0-30, 30-50 y 50- 80 cm, con el fin de determinar la masa de raíces, y la concentración y contenido de nutrientes en cada cobertura vegetal. La masa de raíces finas disminuyó rápidamente a medida que aumentaba la profundidad, encontrándose en la parcela de ciprés el 83 % de las raíces en los primeros 30 cm de profundidad, en pino pátula el 75 % y en roble el 68 %. Los elementos con mayor participación en las raíces finas fueron calcio y potasio, siendo el primero de ellos mucho mayor en la cobertura de ciprés con respecto a las parcelas restantes, seguido en abundancia del potasio, a excepción de la parcela de roble en donde la concentración de un oligoelemento como Fe, fue incluso superior a la de calcio. Los elementos Ca, Mg, K, P, Mn, Cu y Zn acumulados en las raíces finas, hasta los 80 cm de profundidad, fueron superiores en la cobertura de ciprés, con la única excepción de Fe, que fue superior en la parcela de roble. En las parcelas de pino pátula y ciprés, el patrón de abundancia siguió la secuencia decreciente Ca > K Mg > Fe > P. En este trabajo se pretendió resaltar la importancia de las raíces finas y la concentración de los elementos, en los ecosistemas forestales naturales y plantados y su relación con el ciclo de nutrientes. Para ello, la aproximación metodológica comprendió la masa total de raíces, esto es raíces vivas y muertas en conjunto. In the Piedras Blancas region, Antioquia-Colombia, a sampling of fine roots (£ 5 mm) was conducted in three permanent plots established in forest ecosystems of pine (Pinus patula Schltdl), cypress (Cupressus lusitanica Mill) and oak (Quercus humboldtii Bonpl.), at different depths: 0-30, 30-50 and 50- 80 cm, in order to determine the mass of roots and the concentration and content of nutrients in each vegetation type. The mass of fine roots diminished quickly as depth increased, representing in the cypress plot 83 % of all roots in the first 30 cm of depth, in pine 75 %, and in oak forest 68 %. The elements with the highest participation in the fine roots were calcium and potassium, with the former much greater in the cypress cover compared to the other plots, continuing in abundance potassium, with the exception of the oak plot where the concentration of Fe microelement was even greater than that of calcium. The elements Ca, Mg, K, P, Mn, Cu, and Zn accumulated in the fine roots up to 80 cm of depth were greater in the cypress cover, with the only exception being Fe, which was greater in the oak plot. In pine and cypress plots, the pattern of abundances followed the following sequence Ca > K > Mg > Fe > P. This study sought to highlight the importance of fine roots and their concentrations of nutrients in natural forests and plantations and their relationship with nutrient cycling. For this purpose, the methodological approach comprised total root mass, both dead and alive.

En bosques montanos naturales de roble (Quercus humboldtii Bonpl.) y plantados de pino pátula (Pinus patula Schltdl. & Cham.) y ciprés (Cupressus lusitanica Mill.) de la región de Piedras Blancas, Antioquia (Colombia), fueron medidos los flujos de escorrentía superficial (ES) por un periodo de tiempo de 16 meses. Se implementaron parcelas cerradas de escorrentía superficial de 10 m de largo x 2 m de ancho, tanques colectores y sistemas de registro volumétrico. Los flujos fueron de 23,19 mm año-1 (1,07 % de la precipitación) para la cobertura de roble; 35,13 mm año-1 (1,61 % de la precipitación) para la cobertura de pino pátula y 230,64 mm año-1 (11,05 % de la precipitación) para la cobertura de ciprés. Mediante análisis de componentes principales (ACP) se identificaron las relaciones existentes entre las variables hidrológicas y los flujos de ES, y por medio de análisis de regresión lineal múltiple se ajustaron modelos para los flujos de ES por cobertura en función de la precipitación, la precipitación en el bosque y la intensidad de lluvia promedio, variables que mostraron alta relación con la ES según el ACP. In natural montane oak forests (Quercus humboldtii Bonpl.), in pine (Pinus patula Schltdl. & Cham.) and cypress (Cupressus lusitanica Mill.) plantations in Piedras Blancas, Antioquia (Colombia), surface runoff flows (SRF) were measured over 16 months. Runoff was measured using 10 m long x 2 m wide runoff bounded plots, collector tanks and a volumetric counter system. SRF were 23,19 mm year -1 (1,07 % of rainfall) for oak forest; 35,13 mm year -1 (1,61 % of rainfall) for pine and 230,64 mm year-1 (11,05 % of rainfall) for cypress plantations. Relationships between hydrological variables and SRF were identified by a principal components analysis (PCA). For each one of the stands, multiple regression analysis was used to fit models of SRF on rainfall, throughfall and mean intensity of rainfall, variables that, according to the PCA results, appeared highly related to SRF.

En la región de Piedras Blancas, Antioquia - Colombia, se realizó un muestreo de raíces finas (5 mm) en tres parcelas permanentes establecidas en bosques de pino pátula (Pinus patula Schltdl y Cham), ciprés (Cupressus lusitanica Mill) y roble (Quercus humboldtii Bonpl.) a diferentes profundidades: 0-30, 30-50 y 50-80 cm, con el fin de determinar la masa de raíces, y la concentración y contenido de nutrientes en cada cobertura vegetal. La masa de raíces finas disminuyó rápidamente a medida que aumentaba la profundidad, encontrándose en la parcela de ciprés el 83 % de las raíces en los primeros 30 cm de profundidad, en pino pátula el 75 % y en roble el 68 %. Los elementos con mayor participación en las raíces finas fueron calcio y potasio, siendo el primero de ellos mucho mayor en la cobertura de ciprés con respecto a las parcelas restantes, seguido en abundancia del potasio, a excepción de la parcela de roble en donde la concentración de un oligoelemento como Fe, fue incluso superior a la de calcio. Los elementos Ca, Mg, K, P, Mn, Cu y Zn acumulados en las raíces finas, hasta los 80 cm de profundidad, fueron superiores en la cobertura de ciprés, con la única excepción de Fe, que fue superior en la parcela de roble. En las parcelas de pino pátula y ciprés, el patrón de abundancia siguió la secuencia decreciente Ca and gt; K Mg and gt; Fe and gt; P. En este trabajo se pretendió resaltar la importancia de las raíces finas y la concentración de los elementos, en los ecosistemas forestales naturales y plantados y su relación con el ciclo de nutrientes. Para ello, la aproximación metodológica comprendió la masa total de raíces, esto es raíces vivas y muertas en conjunto.

Forestales-Forestería

El artículo revisa la literatura relativa a los métodos de predicción del sitio forestal con énfasis en las especies tropicales y, en especial, aquellas que se han plantado en Colombia. Luego de definir los conceptos de sitio, índice de sitio y de calidad de sitio, se describen con ejemplos las siguientes cinco aproximaciones para la predicción del sitio: actores climáticos, empleo de la vegetación indicadora, correlación con la fisiografía, correlación con características del suelo y bioensayos.

An egg parasite, Telenomus alsophilae Viereck, from the fall cankerworm, Alsophila pometaria (Harris), in Virginia was established on Oxydia trychiata (Guenee) in the Department of Antioquia, Colombia. A. pometaria is a general defoliator of broadleaved forests in eastern North America, while O. trychiata defoliates the introduced conifers Pinus patula Schiede & Deppe and Cupressus lusitanica Miller in Colombia; O. trychiata also has been reared on several species of broadleaved trees. Within a year, the introduced parasite eliminated O. trychiata in the plantation where it was released. This is the 1st successful application of a biological control agent against a forest insect in Colombia. The behavior of T. alsophilae on eggs of O. trychiata is described, and its life cycle under several environmental conditions and the relationships between host age and successful parasitism are reported. We recommend a program of intensive taxonomic and biological research on the genus Telenomus , particularly in the Western Hemisphere. It has the potential for widespread use in biological control.

Data on stemwood biomass and mean annual biomass increment ( MABI ) for seven tropical tree plantation species were synthesized from the literature to evaluate species adaptibility and potential yields in different environments. Stemwood biomass ranged from MABI ranged from about 1 to 30 t ha−1 year−1 in plantations of Pinus caribaea, Tectona grandis, Pinus patula, Gmelina arborea, Cupressus lusitanica, Eucalyptus grandis, and Albizia falcataria. Stemwood biomass and MABI varied with species, plantation age, and climate. Linear models best described the relationship between stemwood biomass and age of plantation, and the slopes of these equations ( MABIs ) varied among species and among life zones for a given species. Significant relations were found between stemwood biomass and MABI and water availability (the ratio of temperature to precipitation, T/P). In general, stemwood biomass and MABI decreased at high (arid) and low (very humid) T/P ratios. Each tree species had an optimal T/P at which its maximum stemwood biomass and MABI occurred. Other site factors, such as soil fertility, modified plantation response to climate.

The effect of unsterile soil leachates on the colonisation by Armillaria mellea of cylinders of Pinus patula and Cupressus lusitanica was studied and is discussed with relevance to East Africa.

Eighty-three plantations and adjacent natural forest stands in highland Ethiopia were analysed for herbaceous plant cover and biomass, species richness, and soil physical and chemical characteristics, in order to reveal the impact of plantation establishment. Climatic (temperature and rainfall) and altitudinal control over the distribution of herbaceous plant species in the forests was exposed by canonical correspondence analysis, and the areas of sampling were segregated on the basis of the gradients this revealed. Sites at higher altitudes were characterized by tall trees with large basal area, and by soil with a high organic matter, high N content and low pH. In contrast to the frequent view of eucalypts as harmful for understorey plants, the richness and biomass of herbaceous plant species in plantations of Eucalyptus spp., and also of Pinus patula, was as high as that of natural forests. However, most of the herbs in the plantations were widespread species, mainly weeds or species invading from montane or wooded grassland. The herbaceous vegetation in Cupressus lusitanica plantations older than 9 years was distinct in composition, less diverse, and much reduced in terms of cover and biomass compared with similarly aged plantations of Eucalyptus globulus, E. grandis, E. saligna, Pinus patula and with natural forests. Cupressus lusitanica should therefore not be planted because of the risk of soil erosion. The overall soil characteristics of the natural forests differed from those of the five most common plantation tree species, as revealed by redundancy analysis. Natural forest soil had a higher content of total N, available P and exchangeable Ca (in the case of P as much as 4-25 times higher), possibly owing to a combination of loss of organic matter during conversion of natural forest to plantations, increased leaching in young plantations, and low nutrient demand by natural forest trees as compared with fast-growing exotics.