Effects of vapour pressure deficit and soil water content on leaf water potential between selected provenances of Eucalyptus microtheca in an irrigated plantation, eastern Kenya

Summary

Nitrogen balance in soil under eucalyptus plantations

An understanding of the role of organic nitrogen (N) pools in the N supply of eucalyptus plantations is essential for the development of strategies that maximize the efficient use of N for this crop. This study aimed to evaluate the distribution of organic N pools in different compartments of the soil-plant system and their contributions to the N supply in eucalyptus plantations at different ages (1, 3, 5, and 13 years). Three models were used to estimate the contributions of organic pools: Model I considered N pools contained in the litterfall, N pools in the soil microbial biomass and available soil N (mineral N); Model II considered the N pools in the soil, potentially mineralizable N and the export of N through wood harvesting; and Model III (N balance) was defined as the difference between the initial soil N pool (0-10 cm) and the export of N, taking the application of N fertilizer into account. Model I showed that N pools could supply 27 - 70 % of the N demands of eucalyptus trees at different ages. Model II suggested that the soil N pool may be sufficient for 4 - 5 rotations of 5 years. According to the N balance, these N pools would be sufficient to meet the N demands of eucalyptus for more than 15 rotations of 5 years. The organic pools contribute with different levels of N and together are sufficient to meet the N demands of eucalyptus for several rotations.

Microbial biomass and activity in litter during the initial development of pure and mixed plantations of Eucalyptus grandis and Acacia mangium

Studies on microbial activity and biomass in forestry plantations often overlook the role of litter, typically focusing instead on soil nutrient contents to explain plant and microorganism development. However, since the litter is a significant source of recycled nutrients that affect nutrient dynamics in the soil, litter composition may be more strongly correlated with forest growth and development than soil nutrient contents. This study aimed to test this hypothesis by examining correlations between soil C, N, and P; litter C, N, P, lignin content, and polyphenol content; and microbial biomass and activity in pure and mixed second-rotation plantations of Eucalyptus grandis and Acacia mangium before and after senescent leaf drop. The numbers of cultivable fungi and bacteria were also estimated. All properties were correlated with litter C, N, P, lignin and polyphenols, and with soil C and N. We found higher microbial activity (CO2 evolution) in litter than in soil. In the E. grandis monoculture before senescent leaf drop, microbial biomass C was 46 % higher in litter than in soil. After leaf drop, this difference decreased to 16 %. In A. mangium plantations, however, microbial biomass C was lower in litter than in soil both before and after leaf drop. Microbial biomass N of litter was approximately 94 % greater than that of the soil in summer and winter in all plantations. The number of cultivable fungi and bacteria increased after leaf drop, especially so in the litter. Fungi were also more abundant in the E. grandis litter. In general, the A. mangium monoculture was associated with higher levels of litter lignin and N, especially after leaf drop. In contrast, the polyphenol and C levels in E. grandis monoculture litter were higher after leaf drop. These properties were negatively correlated with total soil C and N. Litter in the mixed stands had lower C:N and C:P ratios and higher N, P, and C levels in the microbial biomass. This suggests more effective nutrient cycling in mixed plantations in the long term, greater stimulation of microbial activity in litter and soil, and a more sustainable system in general.

Fornecimento de cálcio para plantas de eucalyptus saligna por meio de aplicação de resíduo industrial lama de cal

O resíduo industrial lama de cal, originado da produção de papel kraft branqueada de eucalipto, apresenta em sua composição quantidade considerável de cálcio (Ca), o que pode contribuir para reduzir o consumo de fertilizantes em plantios florestais. Com o objetivo de avaliar o efeito da lama de cal como fonte de Ca e seus efeitos sobre a disponibilidade de nutrientes e produção de matéria seca da parte aérea de plantas de eucalipto, foram conduzidos dois ensaios em vasos, em casa de vegetação, na área de pesquisa da Klabin Florestal do Paraná. Os solos utilizados foram um Neossolo Quartzarênico órtico (RQo) e um Nitossolo Vermelho eutroférrico (NV). Os tratamentos constituíram-se de duas fontes de Ca, calcário dolomítico e lama de cal, e de uma testemunha, sendo identificados como: RQo testemunha, RQo calcário e RQo lama de cal; e NV testemunha, NV calcário e NV lama de cal. O delineamento experimental utilizado foi inteiramente casualizado, com quatro repetições. Para tanto, plantas de Eucalyptus saligna foram mantidas por 126 dias em vasos. Quantificou-se a produção de matéria seca e realizaram-se as análises de folhas e dos solos, por ocasião da coleta das plantas. Os dados revelaram que tanto a adição de calcário dolomítico quanto a lama de cal promoveram o fornecimento de Ca para as plantas de eucalipto, proporcionando aumentos na produção de matéria seca. Os teores de Ca e Na nas folhas de eucalipto foram acrescidos com a adição do resíduo ao solo, em comparação com o tratamento com calcário dolomítico, enquanto os teores de N, P, K e S foram semelhantes. As plantas cultivadas nos tratamentos RQo testemunha e RQo lama de cal apresentaram teores foliares de Mg abaixo da faixa considerada adequada. A adição de lama no solo elevou o pH e as concentrações de Ca e de Na, reduziu o Al trocável e não influenciou na disponibilidade de Mg, fato que pode proporcionar deficiência de Mg às plantas, em solos com baixos níveis desse nutriente, conforme observado neste estudo.

Manganese accumulation and its relation to "eucalyptus shoot blight in the Vale do Rio Doce"

Eucalyptus Shoot Blight in the Vale do Rio Doce (ESBVRD) is an anomaly that leads to reduced growth and, in more extreme cases, to death of eucalyptus plants. Initially diagnosed in plantations in the region of the Vale do Rio Doce, in the State of Minas Gerais, Brazil, this problem has also been found in plantations in other regions of the country and even in other countries. Although the symptoms of this anomaly are well-known, its causes are not yet understood. The aim of this study was to evaluate the cause-effect relationship between accumulation of manganese (Mn) in eucalyptus clones and ESBVRD. Characterization of the environment in areas of greater occurrence of this problem in regard to soil, climate and fluctuation of the water table was undertaken in eucalyptus plantations of the Celulose Nipo-brasileira S.A. (Cenibra) company in the region of the Vale do Rio Doce. Plant tissues were sampled in two situations. In the first situation, diagnosis occurred in the initial phase of the anomaly in clones with differentiated tolerance to the problem; in the second situation, diagnosis was made in a single clone, considered to be sensitive, in two time periods - in the phase with the strong presence of symptoms and in the recovery phase, in areas of occurrence and in areas of escape from the problem. The most ESBVRD-sensitive clone showed much higher (4.8 times higher) leaf Mn contents than more tolerant clones. In plants with the anomaly, Mn leaf contents were greater than 3,070 mg kg-1, much greater than the quantity found in those without the anomaly (734 mg kg-1). In the period in which the symptoms began to wane, there was a sharp decline in leaf Mn contents, from 2,194 to 847 mg kg-1. Manganese content in the above ground part and plant litter (44.4 g ha-1) in the area of occurrence of the anomaly was three times greater than that found in these same components (14.1 g ha-1) in the area of absence of the symptom. Based on the evidence found, such as the existence of environmental conditions favorable to high Mn availability to the plants in the areas of greatest incidence of ESBVRD, greater uptake of Mn in sensitive clones and in plants with symptoms, and a synchronism between the intensity of symptoms of ESBVRD and leaf Mn contents, it may be inferred that temporary excess of Mn in eucalyptus plants is closely related to ESBVRD.

Substituição parcial de fosfato solúvel por natural na implantação de Eucalyptus benthamii e Eucalyptus dunnii no Planalto Sul catarinense

A adubação fosfatada é importante para o crescimento inicial do eucalipto, porque suplementa o solo na fase de maior demanda da cultura. O fosfato solúvel (FS) é a fonte comumente utilizada para esse fim, pois apresenta dissolução rápida no solo; contudo, tem custo mais elevado que os fosfatos naturais (FNs), que por sua vez têm dissolução mais lenta. Este trabalho objetivou avaliar o uso de FN como substituinte parcial do FS para o fornecimento de P para Eucalyptus benthamii e E. dunnii. Foram conduzidos dois experimentos no campo, um com cada espécie, no município de Otacílio Costa, SC, no período de novembro de 2010 a dezembro de 2011. O delineamento experimental utilizado foi de blocos casualizados com parcelas subdivididas, com três repetições. Na parcela principal, testou-se a presença ou ausência do FN (0 ou 60 kg ha-1 de P2O5, usando a fonte FN de Bayovar) e nas subparcelas testaram-se as doses de FS (0, 75; 150; e 300 kg ha-1 de P2O5, usando a fonte superfosfato triplo). Foram realizadas medidas de diâmetro à altura do colo e altura das árvores aos 340 dias, após a aplicação das fontes de P. Os resultados evidenciaram que a adubação fosfatada aumentou o crescimento em diâmetro e altura e incrementou o volume das plantas de E. benthamii e E. dunnii, durante o primeiro ano de cultivo. O E. benthamii foi mais exigente à adubação fosfatada, mas permitiu a substituição parcial da dose de fosfato solúvel por fonte de menor solubilidade. Não houve resposta do E. dunnii à aplicação de fosfato natural, devendo a adubação ser realizada com fosfato solúvel.

Ciclagem e balanço de nutrientes no sistema solo-planta em um plantio de Eucalyptus sp., no Distrito Federal

As espécies do gênero Eucalyptus são as mais plantadas no mundo, tornando-se solução para diminuir a pressão sobre as florestas nativas. Este trabalho objetivou avaliar a biomassa seca e sua distribuição nos diferentes compartimentos das árvores (folhas, galhos, casca, lenho e raízes), bem como examinar o conteúdo de macronutrientes dela e o balanço de nutrientes no sistema solo-planta, em um plantio de Eucalyptus urophylla x E. grandis, aos 60 meses de idade, na Fazenda Água Limpa, no Distrito Federal. Os dados foram obtidos de três árvores de eucalipto, que foram cubadas rigorosamente e tiveram as raízes escavadas até a profundidade de 60 cm. Esses dados foram submetidos à análise estatística pela correlação de Pearson. Grande parte da biomassa seca das árvores foi verificada no compartimento lenho (69,19 %), seguido de raízes (10,15 %), galhos (9,75 %), casca (6,06 %) e folhas (4,85 %). Os maiores teores de macronutrientes foram detectados nas folhas (N = 13,55 g kg-1; P = 1,33 g kg-1; K = 8,52 g kg-1; Ca = 7,12 g kg-1; Mg = 2,44 g kg-1; e S = 1,76 g kg-1), enquanto o lenho apresentou os menores (N = 1,73 g kg-1; P = 0,23 g kg-1; K = 0,34 g kg-1; Ca = 0,20 g kg-1; Mg = 0,03 g kg-1; e S = 0,43 g kg-1). A ordem dos conteúdos totais de macronutrientes verificada para a parte aérea foi: N > K > Ca >S > Mg > P, enquanto para as raízes, N > Ca > K > Mg > S > P. As raízes são responsáveis por acumular aproximadamente 11,90 % dos nutrientes contidos na biomassa das árvores; essa quantidade diminui com o aumento da profundidade. O balanço de nutrientes indica que P e S não são suficientes para um novo ciclo da floresta.

APPRAISAL OF THE SNAP MODEL FOR PREDICTING NITROGEN MINERALIZATION IN TROPICAL SOILS UNDER EUCALYPTUS

The Soil Nitrogen Availability Predictor (SNAP) model predicts daily and annual rates of net N mineralization (NNM) based on daily weather measurements, daily predictions of soil water and soil temperature, and on temperature and moisture modifiers obtained during aerobic incubation (basal rate). The model was based on in situ measurements of NNM in Australian soils under temperate climate. The purpose of this study was to assess this model for use in tropical soils under eucalyptus plantations in São Paulo State, Brazil. Based on field incubations for one month in three, NNM rates were measured at 11 sites (0-20 cm layer) for 21 months. The basal rate was determined in in situ incubations during moist and warm periods (January to March). Annual rates of 150-350 kg ha-1 yr-1 NNM predicted by the SNAP model were reasonably accurate (R2 = 0.84). In other periods, at lower moisture and temperature, NNM rates were overestimated. Therefore, if used carefully, the model can provide adequate predictions of annual NNM and may be useful in practical applications. For NNM predictions for shorter periods than a year or under suboptimal incubation conditions, the temperature and moisture modifiers need to be recalibrated for tropical conditions.

Differential Behavior of Young Eucalyptus Clones in Response to Nitrogen Supply

Eucalyptus requires large amounts of nitrogen (N); however, it responds in diverse manners to the application of this nutrient. The aim of this study was to evaluate the differential performance in growth, mineral nutrition, and gas exchanges of N-fertilized Eucalyptus clones. The treatments consisted of two Eucalyptus clones (VM-01 and I-144) and six N application rates (0, 0.74, 2.93, 4.39, 5.85, and 8 mmol L-1 NH4NO3) arranged in a randomized complete block design with five replications. VM-01 had greater plant height and greater height/collar diameter ratio, as well as higher leaf concentrations of all macronutrients and of Cu, Fe, Mo, and Zn. In terms of total and root dry matter production, root/shoot ratio, and collar diameter, as well as stomatal conductance and transpiration, I-144 performed better. The performance of the clones was clearly differentiated, and the growth of I-144, despite lower leaf N concentration, was in general better than VM-01.

LEAF TOTAL NITROGEN CONCENTRATION AS AN INDICATOR OF NITROGEN STATUS FOR PLANTLETS AND YOUNG PLANTS OF EUCALYPTUS CLONES

The use of leaf total nitrogen concentration as an indicator for nutritional diagnosis has some limitations. The objective of this study was to determine the reliability of total N concentration as an indicator of N status for eucalyptus clones, and to compare it with alternative indicators. A greenhouse experiment was carried out in a randomized complete block design in a 2 × 6 factorial arrangement with plantlets of two eucalyptus clones (140 days old) and six levels of N in the nutrient solution. In addition, a field experiment was carried out in a completely randomized design in a 2 × 2 × 2 × 3 factorial arrangement, consisting of two seasons, two regions, two young clones (approximately two years old), and three positions of crown leaf sampling. The field areas (regions) had contrasting soil physical and chemical properties, and their soil contents for total N, NH+4-N, and NO−3-N were determined in five soil layers, up to a depth of 1.0 m. We evaluated the following indicators of plant N status in roots and leaves: contents of total N, NH+4-N, NO−3-N, and chlorophyll; N/P ratio; and chlorophyll meter readings on the leaves. Ammonium (root) and NO−3-N (root and leaf) efficiently predicted N requirements for eucalyptus plantlets in the greenhouse. Similarly, leaf N/P, chlorophyll values, and chlorophyll meter readings provided good results in the greenhouse. However, leaf N/P did not reflect the soil N status, and the use of the chlorophyll meter could not be generalized for different genotypes. Leaf total N concentration is not an ideal indicator, but it and the chlorophyll levels best represent the soil N status for young eucalyptus clones under field conditions.

Behavior of Eucalyptus urophylla and Eucalyptus citriodora Seedlings Grown in Soil Contaminated by Arsenate

ABSTRACT Persistent areas of tailings and deposits from coal and gold mining may present high levels of arsenic (As), mainly in the arsenate form, endangering the environment and human health. The establishment of vegetation cover is a key step to reclaiming these environments. Thus, this study aimed to evaluate the potential of Eucalyptus urophylla and E. citriodora seedlings for use in phytoremediation programs of arsenate-contaminated areas. Soil samples were incubated at increasing rates (0, 50, 100, 200 and 400 mg dm-3) of arsenic (arsenate form, using Na2HAsO4) for 15 days. The seedlings were produced in a substrate (vermiculite + sawdust) and were transplanted to the pots with soil three months after seed germination. The values of plant height and diameter were taken during transplanting and 30, 60 and 90 days after transplanting. In the last evaluation, the total leaf area and biomass of shoots and roots were also determined. The values of available As in soil which caused a 50 % dry matter reduction (TS50%), the As translocation index (TI) from the roots to the shoot of the plants, and its bioconcentration factor (BF) were also calculated. Higher levels of arsenate in the soil significantly reduced the dry matter production of roots and shoots and the height of both species, most notably in E. urophylla plants. The highest levels of As were found in the root, with higher values for E. citriodora (ranging from 253.86 to 400 mg dm-3). The TI and BF were also reduced with As doses, but the values found in E. citriodora were significantly higher than in E. urophylla. E. citriodora plants presented a higher capacity to tolerate As and translocate it to the shoot than E. urophylla. Although these species cannot be considered as hyperaccumulators of As, E. citriodora presented the potential to be used in phytoremediation programs in arsenate-contaminated areas due to the long-term growth period of this species.

Seletividade alimentar e influência da idade da folha de Eucalyptus SPP. para Thyrinteina Arnobia (Lepidoptera: Geometridae)

Thyrinteina arnobia (Stoll, 1782) (Lepidoptera: Geometridae) é considerada uma das mais sérias pragas do eucalipto no Brasil. Este trabalho foi realizado com o objetivo de estudar a preferência alimentar de T. arnobia em seis espécies de eucalipto e a influência da idade foliar sobre a seleção hospedeira, utilizando-se folhas jovens e velhas de Eucalyptus grandis, Eucalyptus camaldulensis, Eucalyptus saligna, Eucalyptus citriodora, Eucalyptus robusta e Eucalyptus cloeziana. Lagartas de T. arnobia alimentadas na geração anterior com folhas de E. grandis preferiram folhas jovens de E. grandis e E.cloeziana, enquanto as alimentadas com E. saligna, na geração anterior, preferiram folhas velhas de E. grandis. A espécie preferida por lagartas de T. arnobia foi E. grandis, observando-se, também maior preferência por folhas jovens que por folhas velhas nas espécies utilizadas nos testes.

Mycorrhizal colonization and phenolic compounds accumulation on roots of Eucalyptus dunnii maiden inoculated with ectomycorrhizal fungi

Compatibility between Eucalyptus dunnii and the ectomycorrhizal fungi Hysterangium gardneri and Pisolithus sp. - from Eucalyptus spp. -, Rhizopogon nigrescens and Suillus cothurnatus - from Pinus spp.-, was studied in vitro. Pisolithus sp., H. gardneri and S. cothurnatus colonized the roots. Pisolithus sp. mycorrhizas presented mantle and Hartig net, while H. gardneri and S. cothurnatus mycorrhizas presented only mantle. S. cothurnatus increased phenolics level on roots. Pisolithus sp. and R. nigrescens decreased the level of these substances. The isolates from Eucalyptus seem to be more compatible towards E. dunnii than those from Pinus. The mechanisms involved could be related, at least in the cases of Pisolithus and Suillus, to the concentration of phenolics in roots.

Efeito de inoculante ectomicorrízico produzido por fermentação semi-sólida sobre o crescimento de Eucalyptus dunnii Maiden

O crescimento de Eucalyptus é favorecido por fungos ectomicorrízicos (FECM). De ocorrência comum nas plantações florestais, os FECM diferem, entretanto, em infectividade e eficiência. O objetivo deste estudo foi testar a compatibilidade e a eficiência do inoculante ectomicorrízico produzido por fermentação semi-sólida, em relação a Eucalyptus dunnii Maiden. Neste sentido, o inoculante de Pisolithus sp., produzido por fermentação semi-sólida em vermiculita-solução nutritiva, foi aplicado ao substrato turfa-vermiculita (30:70, v/v) nas concentrações de 0, 1, 3, 5 e 10% (v/v) que foi semeado com E. dunnii, e mantido em casa de vegetação. A inoculação proporcionou colonização radicular e aumento da matéria seca da parte aérea e do conteúdo de P em razão da concentração do inoculante. O peso da matéria seca das plantas com 1% de inoculante não diferiu do peso das testemunhas. A 3% e 5%, a matéria seca aumentou 62%. O maior valor foi obtido com 10% de inoculante, onde o peso das plantas foi 73% superior ao das testemunhas, e o teor de P, 130%. Resultados semelhantes foram obtidos em relação à raiz. Altura e diâmetro foram positivamente afetados pela inoculação, mas não a relação raiz/parte aérea. As doses mais eficientes de inoculante foram aquelas de 3% ou superiores. Este método de produção deverá ser testado com outros FECM, e sua eficiência, avaliada em viveiro e no campo.

Toxidez de zinco no crescimento e nutrição de Eucalyptus maculata e Eucalyptus urophylla em solução nutritiva

O objetivo do trabalho foi avaliar o efeito de doses excessivas de Zn no crescimento e nutrição do eucalipto, em casa de vegetação. Mudas de Eucalyptus maculata e Eucalyptus urophylla foram crescidas em vasos contendo 2 L de solução nutritiva de Clark, adicionando-se doses crescentes de Zn: 0, 400, 800, 1.200 e 1.600 miM fornecidas como ZnSO4. Após cinco semanas, as plantas exibiram clorose internerval, escurecimento das raízes e inibição do crescimento, mesmo nas doses mais baixas do metal. A dose crítica de Zn na solução (para redução de 10% na matéria seca da parte aérea) em E. maculata foi de 170,3 miM, e em E. urophylla, 73,0 miM. Os níveis críticos de toxidez de Zn na planta foram de 853 mg kg-1 em E. maculata, e 697,8 mg kg-1 em E. urophylla. Esses resultados indicam que E. maculata é mais tolerante ao Zn do que E. urophylla. Altas doses de Zn reduziram as concentrações de Fe e Ca na matéria seca da parte aérea a níveis considerados deficientes para o crescimento das duas espécies. A translocação de Fe das raízes para a parte aérea foi reduzida, independentemente da espécie, de 21% no controle para apenas 2% em 1.600 miM de Zn, indicando forte relação entre a queda na produção de matéria seca e a ocorrência da deficiência induzida de Fe nas plantas.