Inter-annual variability of precipitation constrains the production response of boreal Pinus sylvestris to nitrogen fertilization

© 2015 Published by Elsevier B.V.Tree growth resources and the efficiency of resource-use for biomass production determine the productivity of forest ecosystems. In nutrient-limited forests, nitrogen (N)-fertilization increases foliage [N], which may increase photosynthetic rates, leaf area index (L), and thus light interception (IC). The product of such changes is a higher gross primary production and higher net primary production (NPP). However, fertilization may also alter carbohydrate partitioning from below- to aboveground, increasing aboveground NPP (ANPP). We analyzed effects of long-term N-fertilization on NPP, and that of long-term carbon storing organs (NPPS) in a Pinus sylvestris forest on sandy soil, a wide-ranging forest type in the boreal region. We based our analyses on a combination of destructive harvesting, consecutive mensuration, and optical measurements of canopy openness. After eight-year fertilization with a total of 70gNm^-2, ANPP was 27±7% higher in the fertilized (F) relative to the reference (R) stand, but although L increased relative to its pre-fertilization values, IC was not greater than in R. On the seventh year after the treatment initiation, the increase of ANPP was matched by the decrease of belowground NPP (78 vs. 92gCm^-2yr^-1; ~17% of NPP) and, given the similarity of IC, suggests that the main effect of N-fertilization was changed carbon partitioning rather than increased canopy photosynthesis. Annual NPPS increased linearly with growing season temperature (T) in both treatments, with an upward shift of 70.2gCm^-2yr^-1 by fertilization, which also caused greater amount of unexplained variation (r²=0.53 in R, 0.21 in F). Residuals of the NPPS-T relationship of F were related to growing season precipitation (P, r²=0.48), indicating that T constrains productivity at this site regardless of fertility, while P is important in determining productivity where N-limitation is alleviated. We estimated that, in a growing season average T (11.5±1.0°C; 33-year-mean), NPPS response to N-fertilization will be nullified with P 31mm less than the mean (325±85mm), and would double with P 109mm greater than the mean. These results suggest that inter-annual variation in climate, particularly in P, may help explaining the reported large variability in growth responses to fertilization of pine stands on sandy soils. Furthermore, forest management of long-rotation systems, such as those of boreal and northern temperate forests, must consider the efficiency of fertilization in terms of wood production in the context of changes in climate predicted for the region.

Allometric analysis of Sitka spruce branches:Mechanical versus hydraulic design principles

The geometry of tree branches can have considerable effect on their efficiency in terms of carbon export per unit carbon investment in structure. The purpose of this study was to evaluate different design criteria using data describing the form of Picea sitchensis branches. Allometric analysis of the data suggests that resources are distributed to favour shoots with the greatest opportunity for extension into new space, with priority to the extension of the leader. The distribution of allometric relations of links (branch elements) was tested against two models: the pipe model, based on hydraulic transport requirements, and a static load model based on the requirement of shoots to provide mechanical resistance to static loads. Static load resistance required the load parameter to be proportional to the link radius raised to the power of 4. This was shown to be true within a 95% statistical confidence limit. The pipe model would require total distal length to be proportional to link radius squared but the measured branches did not conform well to this model. The comparison suggests that the diameters of branch elements were more related to the requirements for mechanical load. The cost of following a hydraulic design principle (the pipe model) in terms of mechanical efficiency was estimated and suggested that the pipe model branch would not be mechanically compromised but would use structural resources inefficiently. Resource allocation among branch elements was found to be consistent with mechanical stability criteria but also indicated the possibility of allocation based on other criteria, such as potential light interception by shoots. The evidence suggests that whilst branch topology increments by reiteration of units of morphogenesis, the geometry follows a functional design pattern.

Exploring options for managing strategies for pea-barley intercropping using a modeling approach

A modeling Study was carried out into pea-barley intercropping in northern Europe. The two objectives were (a) to compare pea-barley intercropping to sole cropping in terms of grain and nitrogen yield amounts and stability, and (b) to explore options for managing pea-barley intercropping systems in order to maximize the biomass produced and the grain and nitrogen yields according to the available resources, such as light, water and nitrogen. The study consisted of simulations taking into account soil and weather variability among three sites located in northern European Countries (Denmark, United Kingdom and France), and using 10 years of weather records. A preliminary stage evaluated the STICS intercrop model's ability to predict grain and nitrogen yields of the two species, using a 2-year dataset from trials conducted at the three sites. The work was carried out in two phases, (a) the model was run to investigate the potentialities of intercrops as compared to sole crops, and (b) the model was run to explore options for managing pea-barley intercropping, asking the following three questions: (i) in order to increase light capture, Would it be worth delaying the sowing dates of one species? (ii) How to manage sowing density and seed proportion of each species in the intercrop to improve total grain yield and N use efficiency? (iii) How to optimize the use of nitrogen resources by choosing the most suitable preceding crop and/or the most appropriate soil? It was found that (1) intercropping made better use of environmental resources as regards yield amount and stability than sole cropping, with a noticeable site effect, (2) pea growth in intercrops was strongly linked to soil moisture, and barley yield was determined by nitrogen uptake and light interception due to its height relative to pea, (3) sowing barley before pea led to a relative grain yield reduction averaged over all three sites, but sowing strategy must be adapted to the location, being dependent on temperature and thus latitude, (4) density and species proportions had a small effect on total grain yield, underlining the interspecific offset in the use of environmental growth resources which led to similar total grain yields whatever the pea-barley design, and (5) long-term strategies including mineralization management through organic residue supply and rotation management were very valuable, always favoring intercrop total grain yield and N accumulation. (C) 2009 Elsevier B.V. All rights reserved.

Canopy characteristics of contrasting clones of cacao (Theobroma cacao)

Canopy characteristics (leaf area index, fractional light interception, extinction coefficient) of mature trees of ten clonally propagated cacao cultivars were measured over a period of 14 months at an experimental site in Bahia, Brazil. Differences in leaf area index between clones became more pronounced over time. When an approximately constant leaf area index was reached (after about nine months), LAI varied between clones from 2.8 to 4.5. Clonal differences in the relationship between leaf area index and fractional light interception implied differences in canopy architecture, as reflected by the range of extinction coefficients (mean values ranged from 0.63 for the clone TSH-565 to 0.82 for CC-10). The results demonstrate the potential for breeding more photosynthetically efficient cacao canopies.

Comportamento da tiririca (Cyperus rotundus) sob diferentes níveis de adubação fosfatada e de sombreamento

O trabalho, instalado e conduzido em casa de vegetação da FCAV, campus de Jaboticabal, UNESP, teve por objetivos estudar os efeitos de diferentes doses de adubação fosfatada (0, 33,5, 67,0 e 100,5 ppm de P2O5) e níveis de sombreamento (0, 30, 50 e 70%) sobre parâmetros de crescimento de tiririca (Cyperrus rotundus). Quatro tubérculos previamente brotados foram colocados em cada vaso com capacidade para três litros de solo. Utilizou-se Latossolo Vermelho-Escuro textura média, moderado, distrófico, peneirado. Para efeito de análise estatística, os vasos (parcelas) foram dispostos num esquema inteiramente casualisado, com quatro repetições. Os resultados obtidos mostraram o efeito prejudicial do sombreamento sobre o desenvolvimento da tiririca. Já ao nível de 30%, o sombreamento causou redução na densidade das plantas , principalmente por reduzir o número de bulbos + tubérculos. em conseqüência, houve redução no acúmulo de matéria seca nas diferentes partes da planta, redução esta mais acentuada no sistema subterrâneo (bulbos + tubérculos + raízes), causando incremento nas relações PA/B+T+R e B+T/R. A adubação fosfatada, no entanto, incrementou os parâmetros de crescimento da espécie, principalmente no desenvolvimento das manifestações epígeas, refletido tanto pelo aumento em número quanto em acúmulo de matéria seca.

Structural characteristics and forage mass of Tifton 85 pastures managed under three post-grazing residual leaf areas

The experiment was carried out on Cynodon spp cv. Tifton 85 pastures grazed by sheep under rotational stocking, with the objective of evaluating the structural characteristics as well as the forage mass of the pastures subjected to three grazing intensities in successive cycles. Treatments were composed of three residual leaf area indices (rLAI; 2.4; 1.6 and 0.8), allocated in completely randomized blocks with seven replications, totaling 21 experimental units. Tiller population density, pasture height, leaf area index, forage morphological composition and pasture forage mass were evaluated. The rLAI modified the tiller population density, which increased linearly with decrease in the rLAI of the pastures. Dry masses of leaf blade, stem and dead material were inferior when the rLAI imposed were lower, which resulted in differentiated forage production among the treatments. Tifton 85 pastures grazed by sheep in rotational stocking under tropical conditions with different rLAI show a modified sward structure over successive grazing cycles, mainly by alteration in the height and LAI of the plants at pre-grazing and by light interception post-grazing, which change the tiller population density. The residual leaf area index of 1.6 is the most suitable for pasture management for being equivalent to the heights of entrance and exit of animals on and from paddocks of 33 and 19 cm, respectively, which avoid great accumulation of dead material and excessive stem elongation, in addition to ensuring tillering in the sward.

Assessing the role of vertical leaves within the photosynthetic function of Styrax camporum under drought conditions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Atributos estruturais e produtivos de capim-marandu em resposta à suplementação alimentar de bovinos e a ciclos de pastejo

O objetivo deste trabalho foi avaliar as alterações estruturais e produtivas de capim-marandu (Brachiaria brizantha cv. Marandu) em resposta à suplementação alimentar de bovinos e a ciclos de pastejo. Os níveis de suplementação com concentrado à base de polpa cítrica, milho, farelo de soja e ureia foram 0,2, 0,6 e 1% do peso vivo. O delineamento experimental foi o de blocos ao acaso, com arranjo em parcelas subdivididas no tempo, com os níveis de suplementação nas parcelas e os ciclos de pastejo nas subparcelas. Os efeitos da suplementação alimentar dos animais sobre o pasto foram detectados sobre o índice de área foliar, interceptação luminosa e relação folha/colmo, em pré-pastejo. Os menores valores foram observados na suplementação de 0,2% do peso vivo. No pós-pastejo, a massa de folhas e a relação folha/colmo foram menores com a menor suplementação (0,2%). Os ciclos de pastejo afetaram as características produtivas e estruturais do pasto, bem como os índices morfogênicos do capim-marandu. Apenas a massa de material morto aumentou, enquanto o número e o peso de perfilhos não foi afetado pelos ciclos de pastejo. O pasto de capim-marandu foi influenciado pela suplementação alimentar dos bovinos. Com o suceder dos ciclos de pastejo, do verão para o outono, há redução do crescimento do pasto, com prejuízos à sua estrutura.

Tillering dynamics in Guinea grass pastures subjected to management strategies under rotational grazing

This study was carried out to analyze the tillering profile of Guinea grass (Panicum maximum cv. Tanzania) pastures subjected to two grazing frequencies (time necessary to intercept 90 and 95% of the incoming light) and two post-grazing heights (30 and 50 cm) in the period from November 2005 to October 2006. The experimental design was of completely randomized blocks with three replications, in a 2 × 2 factorial arrangement. At the end of the spring, pastures managed with 90% light interception showed greater tiller appearance rates in relation to pastures managed with 95%, regardless of post-grazing height. In the summer and fall, pastures managed with post-grazing height of 30 cm showed higher tiller appearance rates in comparison with pastures managed at 50 cm, regardless of grazing frequency. Concerning the tiller mortality rates, in the summer, higher values were found for pastures managed at 90/50 and 95/30 (interception/height), intermediate values at 90/30 and lower values in those managed at 95/50. Pastures managed at 90/30, 95/30 and 95/50 in the fall presented greater tiller mortality rates than those managed at 90/50. These differences do not occur in the winter/beginning of spring. The stability index remained above 1 all through the experimental period. All management strategies evaluated are adequate for Guinea grass.

Influência da irrigação, da densidade de plantio e da adubação nitrogenada nas características morfogênicas, estruturais e de produção do capim-tanzânia

This experiment was carried out to evaluate canopy height of guinea grass with 95% of photosynthetic active radiation interception and quantify the nitrogen fertilization influence and plants' density on the morphogenesis and structural characteristics of Tanzania grass. Four doses of N (0, 80, 160 e 320 kg.ha -1), were arranged with three plant densities (9, 25 and 49 plants.m -2), according to 4 × 3 completely randomized design, with three repetitions. Total dry matter (DM) accumulation throughout the experimental period was influenced by nitrogen fertilization and plants' density. In the rainy period, the higher nitrogen fertilization decreased the harvesting intervals, and consequently, increased the number of harvests. The rate of leaf appearance and the phyllochron were influenced only under nitrogen fertilization in the transition period of rainy and dry weather. Tanzania grass canopy height under 95% of light interception was positively influenced because of the plant densities in rainy period and transition period between rainy/drought and drought. Tanzania grass height under 95% of light interception presented variations along the evaluations and the values were higher (near 70 cm) in the rainy period, followed by transition period rain/drought and drought. © 2011 Sociedade Brasileira de Zootecnia.

Produção de forragem de Tifton 85 adubado com nitrogênio e submetido à lotação contínua

The present assay was conducted at the Research and Development of Adamantina, SP, of the Agência Paulista de Tecnologia dos Agronegócios (APTA) - Pólo da Alta Paulista to evaluate the effect of nitrogen fertilization on morphological composition, density of tillers, leaf area index, light interception and herbage accumulation in grazed Tifton 85 subjected to continuous stocking system. The treatments consisted of four levels of nitrogen (0; 100; 200 and 400kg/ha/year of N), arranged in a randomized complete blocks experimental design with four replications. The grasslands of Cynodon cv. Tifton 85 studied influenced the time of evaluation and of nitrogen levels with a marked effect in morphological composition of the pasture, leaf area index, light interception and population density of tillers that were instrumental in the accumulation of forage. It was found a positive linear effect of nitrogen fertilization on the density of vegetative tillers, totals and herbage accumulation nitrogen fertilization had a marked effect on the amount of total and vegetative tillers, leaf area index in light interception and herbage accumulation. The cultivar Tifton 85 has not reached the necessary conditions for crop growth rate maximum when managed under continuous stocking keeping the grass to 10cm tall.

Características morfogênicas e estruturais do capim-xaraés submetido a intesidades de pastejo

The aim of this study was to evaluate the effects of residual leaf area index (rLAI), years of evaluation and grazing cycles on the morphogenetic and structural characteristics of xaraés palisadegrass subjected to grazing intensities in two summers (years of evaluation). The experiment was carried out at the Universidade Estadual Paulista Júlio de Mesquita Filho - UNESP, Campus de Jaboticabal, São Paulo, Brasil and the intensities of grazing were defined by four rLAI: 0.8, 1.3, 1.8 and 2.3. When the canopy intercepted 95% of incident light, the animals were placed on the pasture for grazing and kept until the rLAI target has been reached. Pastures were grazed by non-lactating Holstein cows (Bos Taurus Taurus L.), using the technique of mob-stocking. The morphogenetic and structural characteristics of xaraés palisadegrass respond effectively to weather conditions. There is variability in morphogenetic and structural characteristics in response to years and grazing cycles within years.

Desempenho e composição morfológica de duas cultivares de Brachiaria brizantha submetidas a intensidades luminosas

Pós-graduação em Zootecnia - FMVZ

Dinâmica de carbono e nitrogênio em pastos de capim-xaraés submetidos a diferentes resíduos pós-pastejo

Pós-graduação em Zootecnia - FCAV

Morfogênese, características estruturais e acúmulo de forragem em pastos de capim-Tifton-85 manejados com diferentes IAF residual

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)