A major goal in restoration is to reestablish native plant communities. There are several ways to reestablish species, but for large areas the most logistically feasible approach is to sow seed of desirable species. However, most wetland seeds are buoyant and are extremely difficult to establish in designated areas before floating away. In upland areas, tackifiers have been used to stabilize hill slopes from erosion and to keep seeds in place. The tackifier works as an adhesive that binds the seeds to the soil. However, the use of a tackifier has not been widely employed in wetland restorations, and prior to its broad implementation into wetland restoration practice, it is important to determine if tackifiers will hold up in wetland conditions. In greenhouse studies, we tested the effectiveness of different tackifier types and concentrations on Bolboschoenus maritimus seedling emergence, the influence of soil moisture and flooding on the duration of tackifier effectiveness, the effect of a mulch addition on tackifier effectiveness (Bolboschoenus maritimus, Schoenoplectus acutus and S. americanus), the effectiveness of pre-germination in enhancing Bolboschoenus maritimus seedling emergence using a tackifier, and the effectiveness of tackifier over time. We concluded that the use of a tackifier was effective at keeping seeds from washing away for at least 15 days, a mulch addition did not enhance tackifier effectiveness, and pre-germination did not benefit B. maritimus seedling emergence. The results from this study provide strong evidence that the use of a tackifier could be an effective solution to establish bulrush species in designated areas in wetland restorations.

Tobacco seed performance is traditionally measured as percentage germination at 14 d under controlled laboratory conditions. However, under greenhouse conditions, seed lots with equal 14-d germination may exhibit substantial differences in uniformity of early seedling growth and spiral root incidence that impact the number of usable transplants. A seedling performance index (SPI) was developed to quantitatively describe greenhouse tobacco seedling performance. The 14-d emergence, relative leaf area uniformity, and seedling leaf area determined by computer image analysis were used to calculate the index. Greenhouse tobacco seed trials demonstrated that seed with the Rickard pellet had higher emergence, but the higher spiral root incidence associated with the Rickard pellet lowered the SPI compared to the Cross Creek pellet. Primed seed lots of flue-cured cultivars (NC 72 and NC 71) had a significantly higher SPI than the nonprimed seed lots at one location but not at a second location. Seed lots sown in Premier Pro-Mix TA commercial medium had a higher spiral root incidence, which resulted in a lower SPI compared to Carolina Choice, Carolina Gold, and Sunshine LP5 commercial media. The index quantitatively determined differences in seedling performance under greenhouse conditions not reflected by standard germination tests. Significant differences in the SPI were observed among seed lots with certified 90% germination. The SPI is a simple method to describe seedling performance because the data used to calculate the SPI is obtained from one seed tray image. In contrast, frequent counting and seedling evaluations are involved with standard germination and vigor tests. / Master of Science

The purpose of this study was to investigate seedling recruitment beneath kanuka forest at Tiromoana Bush, North Canterbury. The regeneration of broadleaved tree species is evident throughout Tiromoana Bush. This research aimed to quantify the biotic and abiotic factors influencing the distribution of small and large seedlings of canopy tree species, their relative growth rates, their survival, abundance and composition throughout the forest understorey of Tiromoana Bush. Tiromoana Bush is a forest restoration area of 410 hectares adjacent to the Kate Valley landfill. To determine the future tree species composition at Tiromoana Bush, seedling recruitment, growth and survival was quantified through remeasuring tagged seedlings in 26 permanent vegetation monitoring plots located in the major forest patches at Tiromoana Bush. In addition, seedling data from 78 temporary vegetation survey plots established in three major forest patches were used to assess the influence of different factors on seedling abundance. At Tiromoana Bush, the most common canopy tree species as seedlings in the permanent vegetation monitoring plots was mahoe followed by fivefinger. Mahoe seedling density was significantly affected by canopy openness, distance to seed sources, light index, shrub cover and slope, but not by aspect, basal area and time. For fivefinger, seedlings increased in abundance with time, but the difference was not statistically significant. The relative growth rate of mahoe in the 20-49cm height class (in which most seedlings occurred) was significantly affected by shrub cover, light index and canopy vii openness. Mahoe seedling recruits were significantly affected by light index and canopy openness. Survivability of mahoe was affected by aspect. For fivefinger, individual relative growth rates were significantly affected by canopy openness and light index. Similar results were found for tree species seedlings present in the temporary survey plots provided with mahoe and fivefinger again the most common species, followed by kohuhu. Light index significantly affected golden akeake small seedlings as well as canopy openness. Light index significantly affected ngaio large seedling distribution. Aspect was the only significant factor for kohuhu large seedling distribution. Distance from seed sources significantly affected fivefinger small seedling distribution as seedlings are dependent upon dispersal away from the parent trees. Slope significantly affected the distribution of red matipou small seedlings. The most important environmental attribute influencing seedling abundance is light. This is evident in both the permanent seedling monitoring plots and the temporary vegetation survey plots. Based on data from the temporary vegetation survey plots, mahoe, fivefinger and kohuhu are most abundant suggesting that these three canopy tree species will dominate the forest canopy at Tiromoana Bush once the kanuka starts to senesce.

Las actividades antropogénicas han producido cambios en los ecosistemas alrededor del mundo. En las regiones tropicales de suramérica, la industrialización de las ciudades y el desmonte de los bosques por medio de quemas son las principales actividades que producen y expulsan contaminantes a la atmósfera e inducen cambios en los patrones de deposición de nutrientes y en el clima de los bosques primarios. El nitrógeno (N) y el fósforo (P) son considerados los principales nutrientes que limitan crecimiento en las plantas ya que su disponibilidad es vital para la cadena de producción primaria de los bosques. Por esta razón, cualquier cambio en la disponibilidad de N o P en los suelos probablemente alteraría importantes mecanismos de la dinámica de los bosques tales como el crecimiento y la sobrevivencia. Cambios en el pH de los suelos (acidez), en los ciclos de nutrientes y en la cantidad de nutrientes afectan la disponibilidad de N y P y producen cambios en varios procesos fisiológicos de los árboles. Si bien bajas proporciones de nutrientes depositados han sido descritas para los bosque montanos del sur del Ecuador (ca. 5 kg ha–1 for N, 0.49 kg ha–1 for P), incluso a estos niveles se espera cambios en la estructura y en la dinámica de los bosques a largo plazo. El grado de reacción de los bosques a los cambios en la disponibilidad de recursos es diferente con cada edad, estatus de sucesión natural, tanto como la etapa de vida de las plantas. Las plántulas de árboles (plantas jóvenes) deberían ser más sensibles a responder a cambios en la disponibilidad de nutrientes que los árboles del bosque maduro. Además, cualquier respuesta en la demografía de las plantas es probablemente más visible en las plántulas antes que en el bosque maduro debido a que las plántulas tienen una dinámica más rápida. Por esta razón, yo estudié la dinámica de la regeneración del bosque montano para entender qué procesos relacionados con los nutrientes están involucrados en el crecimiento y el establecimiento de las plántulas en ambos niveles, individual y de la comunidad de especies. El experimento ecuatoriano de manipulación de nutrientes (NUMEX) ha sido diseñado para estudiar los cambios en el bosque montano como respuesta a la moderada fertilización. El experimento ha sido instalado en un gradiente altitudinal en tres principales sitios de estudio (1000 m.s.n.m.: Bombuscaro, 2000 m.s.n.m.: San Francisco, 3000 m.s.n.m.: Cajanuma) dentro del Parque Nacional Podocarpus y de la Reserva San Francisco. El experimento factorial consiste en cuatro bloques que contienen las parcelas experimentales (N, P, N+P, control) en cada sitio de estudio (16 parcelas por elevación). La fertilización ha sido realizada desde el 2008 añadiendo moderada cantidad de fertilizantes (i.e., 50 kg ha–1 y–1 of N and/o 10 kg ha–1 y–1 of P). Para el estudio de la regeneración de las plántulas de especies de árboles, se utilizaron tres diferentes metodologías para evaluar la comunidad de especies y las respuestas de las especies comunes a la fertilización. La primera metodología consiste en el monitoreo de las comunidades de plántulas en el bosque a 2000 m en tres años consecutivos (2011 – 2013). En 192 sub-parcelas de monitoreo (1m2 cada uno) en San Francisco, todas las plántulas y retoños fueron mapeados y etiquetados. Se estimaron y midieron altura, diámetro, herbivoría y producción de hojas en todos los individuos y se contó en número de nuevos reclutados en cada censo. La segunda metodología determinó patrones de alocación de biomasa y la estequiometría de las plántulas de las seis especies comunes a lo largo del gradiente altitudinal. Las siguientes especies naturalmente abundantes fueron cosechadas: Clarisia racemosa y Pouteria torta en Bombuscaro, Graffenrieda emarginata y Palicourea angustifolia en San Francisco and Grafferieda harlingii y Hedyosmum purpuracens en Cajanuma. Morfología (alocación de biomasa, herbivoría y áreas foliares como: SLA, LAR, LA) y estequiometría de las hojas (contenidos de nutrientes y radios de N:P) fueron medidos y analizados. La tercera metodología consiste en un experimento recíproco de transplante de plántulas (STE) dentro de las parcelas experimentales de NUMEX usando como especie focal, Pouteria torta, para evaluar respuestas específicas en el desenvolvimiento de las plántulas después de un año del experimento. Los tres niveles de análisis mostraron respuestas diferentes a la fertilización de la comunidad de especies de plántulas y de las especies comunes. Contrariamente a los bosques bajos, la comunidad de especies en el bosque montano mostró una moderada respuesta a la fertilización. La densidad de los individuos decreció como consecuencia de la adición de nutrientes y como resultado del bajo reclutamiento en las parcelas experimentales, pero la mortalidad de las plántulas no fue afectada. Consecuentemente los mecanismos dependientes de la densidad activados por la absorción de N no mostraron evidencia de ser el principal eje impulsor de cambios en la densidad de las especies. La comunidad de plántulas no mostró crecimiento por la adición de nutrientes a pesar de que las plántulas en los parcelas de N en general fueron siempre más altas con relación a las plántulas de las parcelas control. Sin embargo, la adición de N incrementó la herbivoría en todas las plántulas lo cual podría enmascarar las reales respuestas de crecimiento. Las especies comunes aparentemente están bien adaptadas a los suelos relativamente pobres debido a que las especies no fueron favorecidas por los cambios en los nutrientes del suelo, mostrando pocos o ningún cambio en crecimiento o en la morfología de las hojas. En un largo período de tiempo, las especies comunes perderían su dominancia por ser menos competitivas que las especies de crecimiento rápido. Sin embargo, se necesitaría un período de tiempo de monitoreo largo bajo continua fertilización para producir cambios visibles en la composición de las comunidad. Las respuestas específicas son difíciles de determinar en comunidades ricas en especies. Por ello, se llevó a cabo el análisis de las seis especies más comunes en un estudio complementario al monitoreo de las comunidad de especies de plántulas. Se evaluó la morfología de las hojas y plántulas además de la estequiometría de las hojas en plántulas cosechas en las parcelas experimentales. Ambos nutrientes (N y P), provocaron efectos en los atributos estudiados sugiriendo una estrecha co-limitación de N y P en las especies de árboles en todos los niveles altitudinales. Sin embargo, los radios de N:P y la frecuente respuesta de las especies a la adición del P indicaron que este nutriente podría ser más limitante que el N a lo largo del gradiente. El grado de reacción de las especies estudiadas varía entre las seis especies. Mayor concentración de P en las hojas en relación al N fue evidente en todas las especies menos en Pouteria torta sugiriendo un alto consumo de P en las especies del bosque montano, similar a las respuestas encontradas en otras especies de plantas tropicales después de fertilización con P. El incremento de la herbivoría fue evidente solamente en dos especies aunque las respuestas fueron opuestas en G. emarginata (N y N+P) y en P.angustifolia (P) a 2000 m mostrando que la selección de las plantas por herbivoría es impulsada por la calidad de los recursos. Muchas de las especies estudiadas mostraron alta maximización de la adquisición de recursos debajo del suelo por la acumulación de biomasa en las raíces, con excepción de G. harlingii a 3000 m., la única especies que mostró alocación significativa de biomasa sobre el suelo como respuesta de la adición de nutrientes. Las plántulas de Pouteria torta mostraron un cambio no significativo en el desenvolvimiento de las especies después de un año de fertilización en STE. Pouteria torta está bien adaptada a los suelos pobres, ya que la adición de N y P no alteró las concentraciones foliares de nutrientes. Sin embargo, la adición de N y N+P significantemente incrementó la mortalidad y el crecimiento de diámetro. La adición de P resultó en un incremento de la perdida de área foliar por herbivoría y desplazó la alocación de carbono al crecimiento de las raíces. Estas respuestas indicaron consecuencias en la fuerza de competencia en el sotobosque y el éxito de reclutamiento de Pouteria. Sin embargo, debido a que las respuestas son ambigüas de algunos atributos (crecimiento y herbivoría) y no están relacionadas con mortalidad es difícil establecer predicciones acerca de la futura abundancia de esta especie a largo plazo. En conclusión, estudios complementarios demostraron que la limitación de un único nutriente en las especies de los bosques montanos no ocurre en un ecosistema rico en especies, a pesar de que los nutrientes están fuertemente correlacionados en mecanismos para la supervivencia y crecimiento. Por consiguiente, la fertilización con nutrientes afectaría varios mecanismos y dinámicas en las comunidades de plantas, el resultado de los cuales se desarrollaría en una escala de largo tiempo.

A trade-off between seed size and seed number is central in seed ecology, and has been suggested to be related to a trade-off between competition and colonization, as well as to a trade-off between stress tolerance and fecundity. Large seeds endure hazards during establishment, such as shading, drought, litter coverage and competition from other plants, better than do small seeds, due to a larger amount of stored resources in the seed. Small seeds, however, are numerous and small-seeded species are therefore more fecund. Moreover, a pattern with small-seeded species being associated with open habitats and large-seeded species being associated with closed habitats has been reported in the literature. In this thesis I assess effects of seed size on recruitment, and how relationships between seed size and recruitment may relate to habitat conditions. Seed sowing experiments were performed in the field to assess inter- and intra-specific relationships between seed size and recruitment in open and closed habitats (Paper I and II). Seed removal experiments were performed in the field to assess what effects seed predation may have on a relationship between seed size and recruitment (Paper III). A garden experiment was performed based on contests between larger-seeded and smaller-seeded species, in order to examine different models on co-existence of multiple seed size strategies. The results showed that there was a weak positive relationship between seed size and recruitment in the field, and that this relationship was only weakly and inconclusively related to habitat (Paper I and II). Seed removal was negatively related to seed size in closed habitats and unrelated to seed size in open habitats (Paper III). This indicates that any positive relationship between seed size and recruitment may be an effect of higher seed removal in small-seeded species. However, when grown under controlled conditions in a garden experiment, there was a clear advantage of larger-seeded species over smaller-seeded species (Paper IV). This advantage was unaffected by seed density, indicating that there was no competitive advantage of the larger-seeded species. Instead, indirect evidence suggests that larger-seeded species exhibit higher tolerance to stress. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Accepted.</p><p> </p>

<p>Fungal pathogens likely play an important role in regulating populations of tree seedlings and preserving forest diversity, due to their ubiquitous presence and differential effects on survival. Host-specific mortality from natural enemies is one of the most widely tested hypotheses in community ecology to explain the high biodiversity of forests. The effects of fungal pathogens on seedling survival are usually discussed under the framework of the Janzen-Connell (JC) hypothesis, which posits that seedlings are more likely to survive when dispersed far from the parent tree or at low densities due to pressure from host-specific pathogens (Janzen 1970, Connell 1971). One of the key challenges to assessing the importance of JC effects has been to identify and quantify the effects of the large numbers of potential pathogens required to maintain host diversity. The primary objectives of this research were to (1) characterize the fungi associated with seedling disease and mortality for a number of important southeastern US forest tree species; and (2) determine if these associations are consistent with the Janzen-Connell hypothesis in terms of differential effects on seedling survival.<br></p><p>Culture-based methods and ribosomal DNA (rDNA) sequencing were used to characterize the fungal community in recently dead and live seedlings of thirteen common tree species in a temperate mixed hardwood forest (North Carolina, USA), with the goal of identifying putative seedling pathogens. Cultures were initially classified and grouped into 130 operational taxonomic units (OTUs) using 96% internal transcribed spacer (ITS) sequence similarity; 46% of all OTUs were found only once. Using rarefaction, it was concluded that the richness of the system was not fully sampled and likely included over 200 taxa (based on non-parametric richness estimators). Species richness did not differ between sampling sites or among the five most common hosts sampled. The large ribosomal subunit (LSU) region of rDNA was then sequenced for representative samples of common OTUs and refined identifications using a constrained maximum likelihood phylogenetic analysis. Phylogenetic placement verified strong BLAST classifications, and allowed for placement of unknown taxa to the order level, with many of these unknowns placed in the Leotiomycetes and Xylariales (Sordariomycetes).<br> </p><p>Next, a hierarchical Bayesian model was developed to predict the effects of multiple putative fungal pathogens on individual seedling survival, without forcing the effects of multiple fungi to be additive. The process of disease was partitioned into a chain of events including incidence, infection, detection, and survival, and conditional probabilities were used to quantify each component individually, but in the context of one another. The use of this modeling approach was illustrated by examining the effects of two putative fungal pathogens, <italics>Colletotrichum acutatum</italics> and <italics>Cylindrocarpon</italics> sp. A, an undescribed species of <italics>Cylindrocarpon</italics>, on the survival of five seedling hosts in both a maximum likelihood and Bayesian framework.<br> </p><p>Finally, the model was used to assess the impacts of these fungi on seedling survival, alone and in combination, using data on five potential fungal pathogens and five hosts. Multi-host fungi had differential effects on seedling survival depending on host identity, and multiple infections may impact survival even when single infections do not. Evaluating these interactions among multiple plant and fungal species generates a set of targeted hypotheses of specific plant-fungal combinations that could help us better understand pathogen-driven diversity maintenance at larger scales than previously possible. Building on these results, some recommendations are provided as to how the Janzen-Connell hypothesis can be re-evaluated with respect to host specificity, pathogen distribution, and environmental context.</p> / Dissertation

This project evaluates the survival and initial growth response of oak seedlings produced under special nursery protocols (?enhanced? seedlings) compared to nursery-run oak seedlings of the same species, and the influence of various cultural practices on these same nursery stocks. Survival did not differ significantly between nursery stocks. Significant differences in survival among competition control treatments did occur. Intensive competition control regimes using glyphosate can negatively impact seedling survival if seedlings come in contact with herbicide spray drift.Nursery-run seedlings had significantly greater growth and many were larger than enhanced seedlings after two growing seasons. Height growth was typically greater with seedlings receiving less intensive competition control, while groundline diameter (GLD) growth was greatest with seedlings receiving more intensive competition control. Subsoil and auger planting typically resulted in greater growth than normal hand planting. Fertilization improved growth in certain areas, but the effects diminished after the first growing season.

Continuous cover forestry (CCF), an alternative forest management approach to clearfelling, is increasingly being adopted in the UK. It aims at enhancing stand structural diversity and favouring natural regeneration and subsequent seedling growth below the existing canopy of plantation forests. One area of limited knowledge is the critical level of below-canopy light for the growth of naturally regenerating seedlings. In addition, plant growth beneath canopies is influenced by other factors (e.g. herbivory). Picea sitchensis (Bong.) Carr. (Sitka spruce) seedlings under canopies have been observed to be severely damaged by Elatobium abietinum (Walker) (green spruce aphid) attacks. The combined effects of light availability and insect attack on seedling growth are not well understood, however, this understanding is crucial in order to ensure successful management of regeneration within CCF systems. A controlled experiment, which mimicked different natural understorey light levels along with repeated artificial aphid infestation, was conducted over two years to look at seedling performance through structural and physiological (chlorophyll fluorescence) measurements. Aphid population assessments showed significant increased population density under shaded conditions. Nevertheless, aphid impacts were mainly localised in extent while the impact of light was the major component that described seedling growth. Light was the primary factor affecting the whole-plant biomass, whereas aphids had only localised effects on the total dry weight of older needles and roots, and on leader extension growth. A significant interaction between light levels and presence/absence of aphid infestation was found for main leader extension growth of the seedlings during the second year of the experiment, with lower values at low light levels under infestation. Plant biomass allocation was affected strongly by light, while aphid presence did not result in significant changes. At the leaf physiologylevel, the light environment was found to be the main driving factor affecting photosynthetic response, whilst aphid presence had only a short-term localised effect on photosynthesis. The impact of light levels and aphid presence on seedling growth were also determined at an experimental field site where plots were located across two light regimes typical of CCF conditions in upland UK coniferous forests. The comparison of the photosynthetic response of the seedlings in both the controlled and field experiment highlighted the importance of considering the temporal heterogeneity of the light environment experienced by understorey seedlings in CCF stands, while aphid and aphid x light interaction effects could not be determined due to very low aphid levels during the year. Finally, a pre-existing light model was parameterised to predict the understorey light environment required to promote successful seedling growth in CCF stands. Sensitivity and validation analyses were also performed.

Continuous Cover Forestry (CCF) has become increasingly popular since the early 1990s. CCF utilises several silvicultural techniques in order to promote and enhance forest structural diversity and favours natural regeneration. As CCF is relatively new to the UK there are still areas of knowledge regarding management interventions that need to be improved upon. This study utilises simple models, seedling physiology and a hybrid gap model and applies them to the Glentress Trial Area which has been under transformation from even-aged forestry since 1952. These efforts have led to an improved understanding of thinning interventions and the effects they may have on future stand structure. Since the formation of the Forestry Commission in 1919, clearfell-replant forestry has been the main form of management practiced in the UK. CCF management differs in several respects and is commonly practiced using expert knowledge in Continental Europe. In the UK the knowledge-base is still growing and therefore simple models can prove useful for guiding management. This study investigated the use of the idealised reverse-J and the Equilibrium Growing Stock (EGS). This study found that the reverse-J shaped diameter distribution is maintained at the Trial, Block and sub- Block scale indicating that an irregular structure is being approached. In addition, the diminution coefficient, a parameter of the reverse-J distribution, falls within values typical of continental Europe. Comparison of the actual diameter-frequency distribution against an ideal reverse-J distribution can inform both thinning intensity and which diameter classes to target. The EGS, which is a volume–diameter distribution, examines standing volume and how that volume is distributed across three broad diameter classes. Typical distributions from the Swiss Jura indicate that percentage volume should be split 20:30:50 across diameter classes. The EGS analysis showed that standing volume in the Trial Area is much lower than European values at just 174 m3 ha-1. In addition, the classic 20:30:50 percent split was not observed. The 1990 data set showed a 49:43:8 distribution but by 2008 it was 40:41:19. As natural regeneration is favoured in CCF a better understanding of seedling physiology is essential. This study established open (15-35 m2 ha-1) and closed canopy plots (>35 m2 ha-1). Plot characteristics were recorded and then seedlings were selected for physical measurements, chlorophyll fluorescence and gas-exchange measurements. There were clear differences between the physical characteristics with a mean Apical Dominance Ratio (APR) of 1.41 for the open plots and 0.9 for the closed plots which is consistent with previous studies suggesting an APR of 1 is needed for successful regeneration. The chlorophyll fluorescence measurements showed a linear relationship with PAR. However, although the results of the gas-exchange measurements showed an increase in photosynthetic rates with PAR for open plots, there was no obvious relationship in the closed plots. As a result, the study did not find a linear relationship between photosynthetic rate and chlorophyll fluorescence. Finally a complex, hybrid gap model was used to investigate the effects of management on predicted future stand structure. The hybrid gap model, PICUS v1.41, was parameterised for Sitka spruce. The model was used to explore different management scenarios on stand structure over two time periods; 1954-2008 and 1952- 2075. The output from the group selection with underplanting scenario, which resembled the actual management, produced realistic output that was comparable to the stand characteristics measured during the 2008 assessment. The output from the 1952-2075 runs suggested that thinning to a residual basal area suitable to allow natural regeneration (<30 m2 ha-1) or a group selection with underplanting were the best management options for maintaining structural diversity.

Este experimento avaliou, em casa de vegetação, o desenvolvimento de mudas de cafeeiro produzidas em tubetes, sob o efeito de malhas utilizadas para sombreamento. Os tratamentos utilizados foram a malha negra 50%, conhecida comercialmente como "sombrite" ou "tela preta", considerada padrão para o desenvolvimento destas mudas, e malhas termo-refletoras com quatro diferentes percentagens de atenuação da radiação solar, sendo as malhas 40%, 50%, 60% e 70%. O delineamento experimental adotado foi em blocos casualizados contendo os 5 tratamentos, com 4 repetições, totalizando-se assim 20 parcelas. As parcelas foram representadas por 20 bancadas, cada qual contendo fechamento superior com um tipo de malha para sombreamento, e também fechamento nas laterais, atenuando a radiação solar lateral. Cada parcela foi composta por 175 mudas, sendo 161 para bordadura, e 14 para avaliações. As irrigações, realizadas diariamente, foram implementadas com a utilização de uma barra motorizada semi-automatizada que se deslocava longitudinalmente na casa de vegetação em ambos os sentidos. A lâmina desejada era ajustada de acordo com a velocidade de deslocamento da barra que era regulada por meio de um inversor de freqüência, responsável por este controle. Para monitorar o microclima, foi instalado interiormente a cada parcela um psicrômetro não ventilado e de tempos em tempos foram realizadas medidas de radiação solar global, fotossinteticamente ativa e o saldo de radiação (SR), estabelecendo-se relações de transmissividade global (TRG) e transmissividade fotossinteticamente ativa (TRFA). As variáveis fisiológicas utilizadas para avaliar o desenvolvimento das mudas foram área foliar, altura das plantas, diâmetro do caule, e, ao final do experimento, foram realizadas análises de matéria seca da parte aérea, do sistema radicular e matéria seca total. A avaliação dos dados psicrométricos mostrou que a temperatura do ar pouco variou nas parcelas, assim como a umidade relativa do ar. Com relação a TRG e TRFA, verificou-se que malhas com menor atenuação da radiação solar apresentaram em geral maior transmissividade, conforme esperado. Para a variável saldo de radiação, a presença de interferências ambientais inviabilizou a maior parte dos dados, verificando-se em apenas parte deles uma tendência de maior SR nas malhas 40% e 50%. A avaliação das variáveis fisiológicas mostrou que a área foliar não apresentou diferença significativa entre os tratamentos. Já para altura da planta e diâmetro do caule, verificou-se que as mudas produzidas sob as malhas termo-refletoras 40% e 50% foram superiores àquelas produzidas sob malha negra 50% e malhas termo-refletoras 60% e 70%, respectivamente. Nas avaliações de matéria seca, verificou-se que as mudas produzidas sob as malhas termo-refletoras 40% e 50%, e malha negra 50% acumularam mais matéria seca comparativamente àquelas produzidas sob malhas termo-refletoras 60% e 70%. Assim, nas condições em que desenvolveu-se o experimento, concluiu-se que as malhas termo-refletoras 40% e 50% e negra 50% apresentaram melhores resultados que as malhas termo-refletoras 60% e 70%. / This experiment evaluated, in greenhouse conditions, the development of coffee seedlings produced in plastic tubes, under the effect of screens used for shading. The treatments were black screen 50%, known commercially as "sombrite" or as "black screen", considered standard for the development of these seedlings, and thermo-reflective screens with four different percentages of attenuation of the solar radiation, being meshes 40%, 50%, 60%, and 70%. The adopted experimental delineation was randomized blocks with 5 treatments and 4 replicates, making up 20 parcels. The parcels were represented by 20 benches; each one with superior closing system with one type of screen, and also side closing system, attenuating the side solar radiation. Each parcel was composed by 175 seedlings, from which 161 were used as a border, and 14 used for the evaluations. The irrigation, daily carried out, was implemented with the use of a semi-automated motorized bar that dislocated longitudinally along the greenhouse in both directions. The desired water amount was set in accordance to the bar displacement speed that was established by means of a frequency inverter, responsible for this control. To monitor the microclimate, one psicrometer was installed inside each parcel and, from time to time, global solar radiation, photosynthetically active radiation, and net radiation (SR) measures were taken, establishing, this way, relations of global transmissivity (TRG) and photosynthetically active transmissivity (TRFA). The physiological variables used to evaluate the development of the seedlings were leaf area, seedlings height, and stalk diameter. Analyses on the dry matter of aerial part and root system and total dry matter were carried out at the end of the experiment. The evaluation of the psicrometers data showed that the temperature of air gently varied in the parcels, as well as the air relative humidity. Relating to TRG and to TRFA, it was verified that screens with less attenuation of the solar radiation presented higher transmissivity in general, as expected. For the variable net radiation, the presence of environment interference made most data impracticable, verifying a partial trend of higher SR in the screens 40% and 50%. The evaluation of the physiological variables showed that the leaf area did not present significant difference among the treatments. Yet, it was verified that, for seedlings height and stalk diameter, the seedlings produced under thermo-reflective screens 40% and 50% were superior to those produced under black screen 50% and thermo-reflective screen 60% and 70%. It was also verified that, for the evaluations of dry matter, the seedlings produced under thermo-reflective screens 40% and 50%, and black screen 50% comparatively accumulated more dry matter than those produced under thermo-reflective screens 60% and 70%. Thus, under the conditions where the experiment was carried out, it can be concluded that the thermo-reflective screens 40% and 50% and black screen 50% presented better results than the thermo-reflective screens 60% and 70%.