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Managing eucalyptus trees in agroforestry systems: Productivity parameters and PAR transmittance
Abstract
Agroforestry systems, in which trees and crops are cultivated in rotation, succession, or association with pastures, are alternatives for the sustainable implementation of agriculture. This study estimated the productive characteristics from eight years old eucalyptus trees in different agroforestry systems and transmission of photosynthetically active solar radiation (PAR). These were composed of a pasture of palisade grass (Urochloa brizantha “BRS Piatã”) and eucalyptus trees (Eucalyptus urograndis “GG100”) planted in April 2011 in single rows 15 m apart with 2 m in-row spacing, totaling 333 trees ha⁻¹. In 2016, half of the trees were thinned, and the spacing was changed to 15 × 4 m. The two systems were then evaluated using an integrated crop-livestock-forestry system (agrosilvopasture with pasture renewal, ICLF) and an integrated livestock-forest system (silvopasture with no pasture renewal, ILF). Each system had 12 paddocks of 5000 m². In ICLF, pasture was renewed in one-third of each replication of area (two paddocks) per crop year, where the grass was simultaneously sown with corn for silage. Pasture renewal was carried out in the 2013–2014, 2014–2015, 2016–2017, and 2017–2018 growing seasons. Data were collected in April 2016 and June 2019, when 110 trees were harvested to determine wood volume and 28 to gather wood rings and samples of the canopy, roots, and carbon content. These data were used to build the equations for estimating stem volume (m³ tree⁻¹) and tree biomass (kg tree⁻¹). Stem diameter at breast height (DBH, 1.3 m above the ground) and tree height (H) were measured in 10% of the trees in each plot to estimate stem volume and biomass; these were compared by t-test (5%). PAR was measured continuously from 2013 to 2019 at 70 cm aboveground with linear quantum sensors at the four ICLF positions across the tree line. Using these data, equations for volume = exp[(− -10.21 + 1.68 × ln(DBH)+1.29 × ln(H)] and biomass = exp[−3.88 + 2.41*ln(DBH)+0.62 × ln(H)] were built. The stem volume was greater in ICLF (225.7 m³ ha⁻¹) than in ILF (215.2 m³ ha⁻¹) (p = 0.0369). The total biomass was 148.3 Mg ha⁻¹ for ICLF and 141.0 Mg ha⁻¹ for ILF, with no significant differences between systems. The agroforestry systems accumulated 64.5 Mg ha⁻¹ of carbon in tree biomass by eight years after system implementation. The basal area of trees in both agroforestry systems showed a strong relationship with the transmission of PAR to the pasture.
... According to Pezzopane et al. (2021), integrated systems with the presence of trees have a high productive potential and capacity to remove atmospheric C and mitigate GHG emissions, where E. urograndis with eight years and density of 167 trees per hectare showed a total biomass of 9.175 Mg ha -1 yr -1 and C stocks in the stem of 4.125 Mg ha -1 yr -1 . Müller et al. (2009), using different species in silvopastoral system with 10 years and population density of 105 plants hectare, estimated the stem biomass of 2.481 Mg ha -1 yr -1 and C stocks of 1.117 Mg ha -1 yr -1 for E. grandis, and biomass accumulation of 1.28 Mg ha -1 yr -1 and C stocks of 0.58 Mg ha -1 yr -1 for U. brizantha. ...
... According to previous studies, the potential of C accumulation in the trees of integrated systems is related, among other factors, to the species, the population density and the entry of light into the system. In addition, integrated systems, as reported by Pezzopane et al. (2021), have the potential to sequester C, which, depending on the destination of wood, can store the C in the biomass for long periods. Santana et al. (2016), evaluating the productivity of E. urograndis in silvopastoral system and monoculture, found the highest average volume of wood per tree, around 0.2228 m 3 (111.4 ...
Agrosilvopastoral systems have been used as sustainable production models that can promote soil organic carbon (SOC) storage. However, there are no simulation studies with the Century model to estimate the SOC accumulation capacity in the long term, analyzing the effects of management and climate change in integrated crop-livestock-forest (ICLF) systems. This study aimed to simulate soil C dynamics in two chronosequences of land-use composed of native vegetation (NV), degraded pasture (DPA) and ICLF system in the Cerrado of Minas Gerais, in addition to designing future scenarios to verify the potential of SOC accumulation through climate change. The results showed that the Century model reliably simulated the SOC stocks in the two chronosequences evaluated. The model predicted an increase in SOC stocks at two sites by converting the DPA system (46.04 and 42.38 Mg ha⁻¹) into ICLF systems (54.94 and 51.71 Mg ha⁻¹). The Century also predicted that a 20 mm decrease in rainfall and a 2 °C increase in temperature in the tropical regions studied could reduce the SOC stocks more expressively in degraded pastures, while agroforestry systems could show a smaller reduction in SOC stocks. In addition, the results showed that replacing degraded pastures into agrosilvopastoral systems, especially in clayey soils, contributes to increasing SOC stocks. Thus, agroforestry systems are potentially viable to maintain the sustainability of agriculture in the face of climate change.
Keywords
agroforestry; climate change; land-use change; soil organic matter
... Such systems are characterized by integrating agricultural, livestock, and forestry activities in the same area in space and time (Nair 1993). Many authors have widely described their benefits, such as increases in soil fertility, soil organic carbon, and soil carbon stock (Da Conceição et al. 2017;Cárdenas et al. 2019;Aryal et al. 2019;López-Santiago et al. 2019), greenhouse gas emission mitigation (Torres et al. 2017;Resende et al. 2020;Pezzopane et al. 2021), animal welfare and thermal comfort improvements (Giro et al. 2019;Pezzopane et al. 2019;Magalhães et al. 2020) and increase in income diversification for farms (Broom et al. 2013). ...
... Knowledge about tree and stand variables in AGSP systems is essential for system management, as it supports planning and decision making by system managers (Tonini et al. 2019;Silva et al. 2020). For example, some studies have found that intercrop yields are significantly negatively correlated with stand basal area (Nissem and Midmore 2002;Comeau and Heineman 2003;Wall et al. 2010;Pezzopane et al. 2021), which is directly related to the diametric distribution. The density and distribution of the trees in an area can also affect the understory growing conditions. ...
The objective of this study was to evaluate height-diameter, volumetric, and taper models to estimate tree height and volume to describe the bole profiles of a eucalypts clone established in three agrosilvopastoral spatial arrangements (18 × 2.5; 5 × 2 + 40; 3 (3 × 2) + 30) in Coronel Xavier Chaves, Minas Gerais state, Brazil. The diameter at breast height, total height, and diameter outside bark along the stems of the sample trees were collected. Height-diameter, volume, and taper models were fit to the observed data for each spatial arrangement and were compared to select the best alternative. The mean annual increment for single, double, and triple lines at 48, 60, and 72 months of age, respectively, ranged from 26.0 to 34.6 m3 ha−1 year−1, as well as individual volume ranged from 0.41 to 0.53 m3 tree−1. The height-diameter curves showed a distinct tendency for each spatial arrangement and can be represented by different equations. The equations to estimate volume and taper fit well to the data, and the Spurr and Garay models were selected as the best fitting, respectively. In addition, Graybill's F-test (Theory and application of the linear model. Duxbury Press, Massachussetts, 1976) showed that a single equation could fit the Spurr and Garay models for all spatial arrangements.
... Chuvas torrenciais atípicas têm ocorrido de forma mais frequente nos últimos anos, e sob insuficiente proteção com biomassa residual os efeitos de erosão podem se agravar, causando sérios danos à conservação do solo. O aumento dos teores de C no solo (Bernardi et al., 2020) e C fixado nas árvores (Pezzopane et al., 2021), em arranjos de SIPA com árvores, mitigam as emissões de Gases de Efeitos Estufa (GEE) gerados pela atividade pecuária. Estudos têm demonstrado que esses sistemas integrados têm a capacidade de neutralizar a emissão de metano entérico pelos animais somada a de óxido nitroso e CO 2 pelo solo, ou mesmo tornar o balanço de carbono positivo no agroecossistema . ...
... Estudos têm demonstrado que esses sistemas integrados têm a capacidade de neutralizar a emissão de metano entérico pelos animais somada a de óxido nitroso e CO 2 pelo solo, ou mesmo tornar o balanço de carbono positivo no agroecossistema . Sistemas com 250 a 350 árvores de eucalipto ha -1 , planejados para corte das árvores aos oito a doze anos de idade, são capazes de produzir 25 m 3 ha -1 ano -1 de madeira (Ofugi et al., 2008;Pezzopane et al., 2021), o que corresponde a um sequestro anual de cerca de 5 Mg ha -1 de C ou 18 Mg ha -1 de CO 2 equivalente -somente pelos troncos -neutralizando a emissão de GEE de cerca de 12 bovinos adultos (Almeida et al., 2011). ...
... Para reduzir o impacto ambiental sobre as florestas, é essencial que os pecuaristas disponham de opções sustentáveis como intensificação do crescimento das pastagens e da produção pecuária (MAZZETO et al., 2015), além da manipulação da fermentação entérica (USEPA, 2022), e, uma outra forma de reduzir as emissões dos GEE é através do aumento dos teores de carbono (C) no solo (BERNARDI et al., 2020) e C fixado nas árvores (PEZZOPANE et al., 2021), em arranjos de sistemas integrados de produção agropecuária com árvores. Esses sistemas integrados têm a capacidade de neutralizar a emissão de metano entérico pelos animais somada a de óxido nitroso (N2O) e dióxido de carbono (CO2) pelo solo, ou mesmo tornar o balanço de carbono positivo no agroecossistema . ...
Methane (CH4) is the second most abundant greenhouse gas (GHG), while CO2 is strongly associated with the long-term evolution of global average temperature, CH4 interferes in the warming of the planet at the instant it is emitted, therefore its role is determinant in the dynamics of the short-term evolution of temperature increase. The main objective of this study is to investigate the effects of intensification of livestock production systems, including their integration, on enteric CH4 emission efficiency indices. A total of 40 experimental animals per year, of the Nellore breed (Bos taurus indicus) with 375±30 kg live weight and 15 to 16 months of age were used, being four animals in each treatment per year: one fistulated animal for rumen fermentation data collection, one animal for performance evaluation and two animals for enteric methane production measurements (SF6 - sulfur hexafluoride - tracer gas technique), distributed in five treatments with two repetitions each, having in each treatment per year, four animals called testers. . The treatments were composed of five different grazing systems and their replicates, as follows: 1) degraded pasture (DP); 2) dryland pasture with moderate animal density (DMS); 3) dryland pasture with high animal stocking rate (DHS); 4) forest livestock system with moderate animal stocking rate (LF); and 5) irrigated pasture with high animal stocking rate (IHS). Grazing units were considered experimental units for data obtained per area, and animals experimental units for data obtained per animal. The model includes the effect of treatment (five grazing systems), seasons (spring, summer, fall, and winter), and the interaction between treatment and seasons as a fixed effect, and year was considered a random effect. Within the presence of interaction, the effects of one factor within the other were evaluated using the SLICE Mixed Procedure command. All means were presented as least squares means and the effects of treatments were separated by the PDIFF option of SAS. Effects were considered significant at P≤ 0.05 by Fisher's LSD test. It is emphasized that pasture production systems, with Nellore animals raised on pasture throughout the entire period of their productive life, intensified with fertilization and soil correction, medium to high stocking rate, with controlled animal stocking during the summer, when there is greater production and availability of forage, such as the DMS and IHS systems, have low methane emission when expressed in production variables such as weight gain and stocking rate: DMS (579.16 gCH4/kg. day-1 and 75.17gCH4/UA.ha.day-1) and IHS (365gCH4/kg.day-1 and 65.62gCH4/UA.ha.day-1), in analogy to data found in the literature. Regarding the gross energy lost in the form of methane, in the DMS system it was lower during the summer (YM = 2.91%), since its consumption (9.92 kg) during the summer was high along with the high stocking rate systems, thus making it an efficient system. In addition, systems such as DMS, for low fertility soils, have the ability to mitigate 145 times more than the integrated system such as LF or up to 25 times as DP, since the LF system did not receive treatment of thinning trees throughout the year. However, when there is interaction between season and system, some variables such as CH4_FDN, CH4_HA_ANO, YM are higher during winter in IHS and lower during spring in LF. During spring, variables such as CH4_GMD, CH4_MSD, CH4_CMS, CH4_FDN and CH4_HA_ANO obtained the lowest results. However, integrated systems are necessary to maintain nutrient cycling, system biodiversity, and animal, plant, and environmental balance. In addition, the modulation of rumen fermentation through the higher CMS, weight gain, efficiency in the rate of food passage through the gastrointestinal tract and consequent reduction of energy loss, provided by proper management of pastures respecting the practices for each season of the year, ensures the quality of these, along with correct fertilization and adequate stocking rate, and has the ability to improve the efficiency of greenhouse gas emissions.
... A presença do componente arbóreo amplia a capacidade de produção de biomassa nos sistemas, em função do potencial de produção das árvores. Em um experimento de ILPF com eucaliptos (Eucalyptus urograndis Clone GG100), numa avaliação da biomassa total das árvores (parte aérea e raiz), aos oito anos de idade das árvores, Pezzopane et al. (2021) quantificaram que as árvores aportaram aos solos taxas anuais de18,58 Mg MS ha -1 ano -1 em um sistema de ILPF e 17,63 Mg MS ha -1 ano -1 em um sistema de IPF (Silvipastoril). ...
Os sistemas integrados de produção são estratégias de uso sustentável da terra, que podem apoiar o aumento da produção agrícola e, ao mesmo tempo, recuperar e preservar o meio ambiente. A adoção dos sistemas integrados representa um avanço significativo na busca da sustentabilidade da agricultura brasileira. As alterações promovidas pelos sistemas integrados nas propriedades físicas, químicas e biológicas do solo refletem na quantidade e qualidade do carbono orgânico. Nos resultados de estudos aqui apresentados, os autores avaliaram a dinâmica, aspectos estruturais e reatividade da matéria orgânica nesses sistemas integrados. Dessa forma foram discutidas como estas informações são fundamentais para compreender os processos que influenciam no acúmulo do C nos solos. Também foi comprovado que sistemas integrados promovem maior acúmulo de C no solo e aumento da estabilidade da matéria orgânica. Os estudos ainda confirmaram a importância desses sistemas para a agricultura sustentável, combate às mudanças climáticas e por ser uma das importantes estratégias do país para a descarbonização da agropecuária. Por fim, sugere-se que estudos sobre a quantidade, qualidade e estrutura das frações da matéria orgânica nos solos, sob sistemas integrados, sejam conduzidos para as diferentes combinações de sistema integrados nos diferentes biomas.
Integrated production systems are sustainable land-use strategies that can support increased agricultural production and, at the same time, recover and preserve the environment. Adopting integrated systems represents a significant advance in the quest for sustainability in Brazilian agriculture. The alterations promoted by the integrated systems in the soil's physical, chemical, and biological properties reflect the quantity and quality of the organic carbon. In the results of the studies presented here, the authors evaluated the dynamics, structural aspects, and reactivity of organic matter in these integrated systems. Thus, it was discussed how this information is fundamental to understanding the processes that influence C accumulation in soils. It has also been proven that integrated systems promote the more significant accumulation of C in the soil and increase the stability of organic matter. The studies also confirmed the importance of these systems for sustainable agriculture, combating climate change, and being one of the country's essential strategies for decarbonizing agriculture and livestock. Finally, it is suggested that studies on the quantity, quality, and structure of organic matter fractions in soils under integrated systems be conducted for different combinations of integrated systems in different biomes.
... Tais sistemas caracterizam-se por integrar as atividades agrícolas, pecuárias e florestais em uma mesma área, em cultivo consorciado, em sucessão ou rotacionado, buscando efeitos sinérgicos entre os componentes do sistema (Balbino et al., 2011). Os benefícios ambientais e produtivos destes sistemas são amplamente descritos por diversos autores, como aumento da fertilidade do solo, carbono orgânico do solo e estoque de carbono do solo (Conceição et al., 2017;Cárdenas et al., 2019;Aryal et al., 2019;López-Santiago et al., 2019), mitigação de emissões de gases de efeito estufa (Torres et al., 2017;Resende et al., 2020;Pezzopane et al., 2021), melhorias no bem-estar animal e conforto térmico (Oliveira et al., 2018;Améndola et al., 2019;Giro et al., 2019;Pezzopane et al., 2019;Magalhães et al., 2020) e aumento da diversificação da renda das fazendas (Broom et al., 2013). ...
O objetivo deste trabalho foi avaliar a adotabilidade de diferentes
modalidades de sistemas de Integração Lavoura-Pecuária-Floresta (ILPF) entre pecuaristas do estado de Mato Grosso do Sul (MS). O trabalho foi conduzido em dois municípios inseridos em duas situações distintas: uma região com predominância na produção de grãos, no centro sul do estado, onde o sistema mais difundido é o de Integração Lavoura-Pecuária (ILP), sem o componente florestal, e outra região com predominância da pecuária na região central, onde o maior potencial de inovação é a Integração Pecuária-Floresta (IPF), pela introdução do componente florestal. Em cada município foi realizada uma oficina com especialistas, profissionais da assistência técnica, gestores de cooperativas, empresas do agronegócio e pesquisadores da região, para a coleta de informações e a aplicação da
metodologia ADOPT. Os públicos-alvo e as tecnologias a serem avaliadas foram definidos previamente com o auxílio de representantes das instituições participantes das oficinas. Cada uma delas contou com a participação de aproximadamente 16 pessoas divididas em dois grupos, sendo que um grupo tratou de questões relativas ao perfil do público-alvo (produtores) e o outro das questões relativas à inovação tecnológica. Foram observadas taxas de adoção superiores a 90% em todas as simulações. Entretanto, alguns gargalos foram identificados: no sul do MS,
dificuldades com assistência técnica especializada foram apontadas como desfavoráveis à adoção da ILP. A IPF, por sua vez, mostrou-se dependente de um modelo de fomento que assegure rentabilidade no curto prazo.
... In extended agrosilvopastoral systems, some crops (rice, barley, soy) can be used in rotation or during the initial years after tree plantation (Souza et al. 2012). Trees protect the crops and pastures against adverse environmental conditions (shading, reduced evapotranspiration, improved soil water availability), mitigate negative environmental impacts on pasturelands (erosion) and contribute to reduce the carbon footprint (Pezzopane et al. 2021). The combinations with pastures and crops increase the overall land productivity balancing the costs of planting and maintaining the stands of eucalyptus (Bosi et al. 2020). ...
The objective of the study was to evaluate the nutritional value of leaves from five eucalyptus species (Eucalyptus astringens, E. leucoxylon, E. sideroxylon, E. lehmannii, E. camaldulensis), harvested in Tunisia (two locations) during the autumn, winter, and spring seasons. Chemical composition and digestibility (various in vitro procedures) and in vitro tannin biological activity were determined. The species E. lehmannii had the lowest neutral detergent fiber (NDF) and lignin contents (252 and 92 g kg⁻¹ dry matter (DM), respectively) and the highest non-fibrous carbohydrates content (553 g kg⁻¹ DM), while the species E. leucoxylon and E. camaldulensis had the highest NDF concentrations (375 and 356 g kg⁻¹ DM, respectively). Among the seasons, higher levels of NDF and lignin were observed in winter (349 and 129 g kg⁻¹ DM, respectively). The species E. sideroxylon showed the highest gas production with polyethylene glycol addition and thus the highest biological tannin activity. The species E. lehmannii and E. camaldulensis had the highest metabolizable energy concentrations, with 6.20 and 6.07 MJ kg⁻¹ DM, respectively. E. camaldulensis showed the highest (37.9%) and E. lehmannii the lowest (31.9%) organic matter digestibility. Foliage from eucalyptus trees are of limited energy and protein value as an alternative fodder for ruminants, with a substantial variability across species. No remarkable seasonal variations in chemical composition and digestibility of eucalyptus foliage were detected.
... Chuvas torrenciais atípicas têm ocorrido de forma mais frequente nos últimos anos, e sob insuficiente proteção com biomassa residual os efeitos de erosão podem se agravar, causando sérios danos à conservação do solo. . Sistemas com 250 a 350 árvores de eucalipto ha -1 , planejados para corte das árvores aos oito a doze anos de idade, são capazes de produzir 25 m 3 ha -1 ano -1 de madeira (Ofugi et al., 2008;Pezzopane et al., 2021), o que corresponde a um sequestro anual de cerca de 5 Mg ha -1 de C ou 18 Mg ha -1 de CO 2 equivalente -somente pelos troncos -neutralizando a emissão de GEE de cerca de 12 bovinos adultos (Almeida et al., 2011). ...
Integrated Agricultural Production Systems (SIPA) are promising strategies to intensify production through activities in the intermediate portion between organic and intensive/specialized agriculture, which must be planned to allow synergistic interactions between soil, plants, and animals. SIPA has been identified as essential to tackle food and energy insecurity and, additionally, to save areas of native vegetation for carbon storage and biodiversity. SIPA research has grown exponentially in Brazil, and these studies demonstrate that integrating crops such as pastures and trees in space or time has improved the efficiency of land and natural resource use. This chapter addresses several current specifications on soil management in LPIS, including the leading strategic practices for building soil fertility, as well as the management of productive components and fertilization of the system with a focus on soil conservation in search of maximizing the return in economic, social, and environmental sustainability.
... There may also be competition for light, soil moisture and nutrients between trees and crops. However, utilization methods of growth response and biochemical effects (allelopathy) are equally interested in poor germination and growth of vicinity vegetation (Singh et al., 2008;Pezzopane et al., 2021). ...
Brassica campestris is a typical daily crop grown all over the world as a source of fodder, vegetables, and oil. The allelopathic effects of Populus nigra L. and Melia azedarach L. extracted leaves on seed germination and growth performance of Brassica campestris L. were studied in the field and in the laboratory. Seeds of Brassica campestris were seeded in pots in the field, whereas seeds sown in tap water were considered as a control. Different leave weight, of both P. nigra L. and M. azedarach was used and mixed with soil separately, to test their allopathic effects. Growth parameters including stem height, stem diameter, leaf number, number of internodes, internodal length, fresh and dry weight of the stem, and 1000 seed-weight were investigated. Number of flowers per plant; and inflorescence size were also considered. The results revealed that all measured parameters of B. campestris were negatively influenced, with the exception of internodal length, which was found to be positively affected. Seeds treated with plant extracts showed an inhibitory effect on seed germination which was directly proportional with doses of leaves weight used. In laboratory experiments, the allelopathic effects of P. nigra aqueous extract on seed germination (%) as well as growth performance of germinated seed, expressed as plumule length and radicle length, of B. campestris were reported. Parallel to the field experiment, a high dose of leaf weight extracted from dried leaves greatly decreased seed germination (%) and growth measured parameters, which are proportional to extracted leaf weight.
... There may also be competition for light, soil moisture and nutrients between trees and crops. However, utilization methods of growth response and biochemical effects (allelopathy) are equally interested in poor germination and growth of vicinity vegetation (Singh et al., 2008;Pezzopane et al., 2021). ...
... There may also be competition for light, soil moisture and nutrients between trees and crops. However, utilization methods of growth response and biochemical effects (allelopathy) are equally interested in poor germination and growth of vicinity vegetation (Singh et al., 2008;Pezzopane et al., 2021). ...
Brassica campestris is a typical daily crop grown all over the world as a source of fodder, length, which was found to be positively affected.Seeds treated with plant extracts showed an seeds sownin tap waterwere considered as a control. Different leave weight,of both P. nigraL. flowers per plant; and inflorescence size were also considered. The results revealed that all length,fresh and dry weightof the stem, and 1000 seedweight were investigated. Number of used. In laboratory experiments, the allelopathic effects of P. nigraaqueous extract on seed leaves on seed germination and growth performanceof Brassica campestris L. were studied in the measured parametersof B.campestris were negatively influenced, with the exception of internodal leaf weight extractedfrom dried leaves greatly decreased seed germination (%) and growth germination (%) as well as growth performanceof germinated seed,expressed as plumule length and radicle length,of B.campestriswere reported. Parallel to the field experiment, a high dose of andM. azedarachwasused andmixed with soil separately, to test their allopathic effects. Growth vegetables, and oil. The allelopathic effects of Populus nigraL. and Melia azedarachL. extracted parameters including stem height, stem diameter, leaf number, number ofinternodes, internodal inhibitory effect on seed germination which was directlyproportionalwith doses of leaves weight field and in the laboratory.Seeds of Brassica campestris were seeded inpots in the field, whereas measured parameters, which are proportional to extracted leaf weight.
... Sarto et al. [52] observed greater carbon sequestration by plant biomass in this agroforestry system compared with the monoculture pasture, mainly by the forest component. Trees increase the potential capacity of integrated systems to remove atmospheric carbon and mitigate greenhouse gas emissions [53]. The most important factor for fostering the storage of soil organic carbon in agroforestry systems is increasing the land equivalent ratio [54] through the vertical and temporal integration of crops and trees and more effective use of sunlight, water, and nutrients [55]. ...
Agroforestry systems integrating tree and forage growth are important for maintaining
soil health but may change the soil’s physical-hydric properties. Our goal was to investigate the impact of introducing Eucalyptus trees into a pasture on the soil water content throughout the soil profile. The study was conducted in a 6-year-old agroforestry system where two species of Eucalyptus were introduced into a palisade grass pasture. Soil moisture was sampled at 0.0 (planting row), 2.0, 4.0, and 6.0 m (midpoint between tree rows) from the Eucalyptus tree rows. A monoculture palisade grass pasture was used as a control. The soil water content down to a depth of 50 cm was lowest in the tree row and increased with distance from the trees. In the Eucalyptus row, the soil water content in the 0–50 cm layer was lower than in the monoculture pasture. Agroforestry systems decreased the water content in the superficial layers of the soil in the rainy months; in the
dry season, the soil water contents in all layers were similar between the Eucalyptus inter-rows. In most seasons, the agroforest systems reduced the forage production close to the Eucalyptus tree rows, up to 2 m from the trees, likely due to the soil water content decrease. Overall, this study showed that in tropical regions with sandy soils, the grass and trees’ competition must be considered when establishing integrated agroforestry systems in order to maximize the advantages and benefits of the diversified agroecosystem.
In integrated crop‐livestock‐forestry (ICLF) systems, an agroforestry model, the forestry component influences the distribution of photosynthetically active radiation (PAR) and alters grain productivity. The aim of this study was to evaluate the effects of systematic and selective thinning of eucalyptus stands on the productivity of soybean and maize grown. The randomized block‐designed experiment comprised three treatments, namely crops grown under full sunlight (CFS) and in ICLF plots subjected to systematic and selective thinning to leave single‐row (ICLF S ) and triple‐row (ICLF T ) tree configurations. Soybean and maize were planted in succession between the tree stands and PAR incidence/transmittance and crop productivities were evaluated in the north and south sun‐exposed faces of the plots during three cultivation cycles after thinning. In comparison with CFS, PAR transmittance in the ICLF systems decrease varied according to the time of day, period of the year, distance of the sampling position from the trees, the sun‐exposed area (north and south faces) and time after thinning. Soybean productivities in ICLF S were similar to those of CFS in the first and second crop cycles, but significantly lower ( p < 0.05) in the third crop cycle. In the ICLF T system, soybean productivity was similar to that of CFS in the second crop cycle but significantly lower in the first and third crop cycles. With regard to the maize crop, productivities decreased in the order CSF > ICLF S > ICLF T in all cultivation cycles. Our results showed that PAR transmittance and soybean/maize productivities were positively influenced by thinning of eucalyptus stands, particularly in ICLF S system.
A superfície topográfica de uma determinada região do planeta pode ser representada por um modelo digital de terreno (MDT) o qual é uma importante fonte de dados cuja utilização se dá para diversos fins, tais como análises de características hidrológicas de bacias hidrográficas. A geração do MDT depende de uma fonte de dados que tenha na sua base valores de elevação da superfície terrestre. Os métodos clássicos para aquisição de dados de superfície e subsuperfície demandam muito tempo, custo ou ainda conhecimentos específicos de processamento para geração do MDT devido ao levantamento topográfico. Assim, o estudo comparou as variações entre as altitudes desses modelos obtidas por quatro fontes de dados, a saber: por meio de imagens capturadas por aeronave remotamente pilotada - drone; imagens capturadas utilizando veículo aéreo tripulado; imagem de satélite; e altitudes obtidas com GPS (Sistema de Posicionamento Global) geodésico, sendo que os resultados para essa análise mostraram que há variação entre os valores dos intervalos de altitude, todavia mesmo com as diferenças observadas nos números, as variações de ambos os MDTs se acompanham ao longo de toda área de estudo.
Brazilian cattle production is mostly carried out in pastures, and the need to mitigate the livestock's greenhouse gas (GHG) emissions and its environmental footprint has become an important requirement. The adoption of well-suited breeds and the intensification of pasture-based livestock production systems are alternatives to optimize the sector's land use. However, further research on tropical systems is necessary. The objective of this research was to evaluate the effect of Holstein (HO) and Jersey–Holstein (JE x HO) crossbred cows in different levels of pasture intensification (continuous grazing system with low stocking rate–CLS; irrigated rotational grazing system with high stocking rate–RHS), and the interaction between these two factors on GHG mitigation. Twenty-four HO and 24 JE x HO crossbred dairy cows were used to evaluate the effect of two grazing systems on milk production and composition, soil GHG emissions, methane (CH4) emission, and soil carbon accumulation (0–100 cm). These variables were used to calculate carbon balance (CB), GHG emission intensity, the number of trees required to mitigate GHG emission, and the land-saving effect. The number of trees necessary to mitigate GHG emission was calculated, considering the C balance within the farm gate. The mitigation of GHG emissions comes from the annual growth rate and accumulation of C in eucalyptus trees' trunks. The CB of all systems and genotypes presented a deficit in carbon (C); there was no difference for genotypes, but RHS was more deficient than CLS (-4.99 to CLS and −28.72 to RHS ton CO2e..ha−1.year−1). The deficit of C on GHG emission intensity was similar between genotypes and higher for RHS (−0.480 to RHS and −0.299 to CLS kg CO2e..kg FCPCmilk−1). Lower GHG removals (0.14 to CLS higher than 0.02 to RHS kg CO2e..kg FCPCmilk−1) had the greatest influence on the GHG emission intensity of milk production. The deficit number of trees to abatement emissions was higher to HO (−46.06 to HO and −38.37 trees/cow to JE x HO) and to RHS (−51.9 to RHS and −33.05 trees/cow to CLS). However, when the results are expressed per ton of FCPCmilk, there was a difference only between pasture management, requiring −6.34 tree. ton FCPCmilk−1 for the RHS and −3.99 tree. ton FCPCmilk−1 for the CLS system. The intensification of pastures resulted in higher milk production and land-saving effect of 2.7 ha. Due to the reservation of the pasture-based dairy systems in increasing soil C sequestration to offset the GHG emissions, especially enteric CH4, planting trees can be used as a mitigation strategy. Also, the land-save effect of intensification can contribute to the issue, since the area spared through the intensification in pasture management becomes available for reforestation with commercial trees.
A intensificação da produção observada no sistema de integração lavoura-pecuária-floresta (ILPF) melhora as condições físicas, químicas e biológicas do solo, aumenta a ciclagem e a eficiência de utilização dos nutrientes, reduz custos de produção, diversifica e estabiliza a renda na propriedade rural e viabiliza a recuperação de áreas com pastagens degradadas. Os sistemas de produção integrados com a presença de árvores são considerados alternativas para a produção sustentável de bovinos de corte. O conceito Carne Carbono Neutro (CCN) visa atestar a mitigação das emissões de metano entérico dos bovinos com o sequestro de carbono pelas árvores em sistema silvipastoril.
The intensification of production observed in the integrated crop-livestock-forest (ILPF) system improves the physical, chemical and biological conditions of the soil, increases cycling and the efficiency of nutrient use, reduces production costs, diversifies and stabilizes income in the rural property and enables the recovery of areas with degraded pastures. Integrated production systems with the presence of trees are considered alternatives for the sustainable production of beef cattle. The Carbon Neutral Meat (CCN) concept aims to attest to the mitigation of enteric methane emissions from cattle with carbon sequestration by trees in a silvopastoral system.
Integrated grazing systems are important to tackle pasture degradation and promote agricultural sustainability, contributing to sustainable development goals and to soil quality. This study aimed to assess physical indicators of soil quality in the topsoil of integrated and non-integrated grazing systems. The studied systems included continuous grazing (CONT), rotational grazing (ROT), integrated crop-livestock (ICL), integrated livestock-forest (ILF), integrated crop-livestock-forest (ICLF) and an adjacent area with native vegetation (NV). The agricultural systems were established by 2011 and the soil was sampled in 2019. Assessments included saturated soil hydraulic conductivity (Ksat), soil bulk density (BD), total porosity (TP), macroporosity (MA), microporosity (MI), soil resistance to penetration (RP), mean weight diameter of soil aggregates (MWD) and total organic carbon (TOC). Apart from MWD, the soil quality indicators were sensitive in differentiating the studied systems. NV accounted for the highest means for Ksat, TP, and MA, and the lowest means for BD, MI, RP and MWD. Ksat in ICLF and ILF was higher than the other grazing systems. The lowest means for TP and MA, and the highest TOC was found in ICLF. BD, TP, MA and RP, which were strongly correlated with each other, suggest a degree of soil compaction in all grazing systems, caused mainly by cattle trampling. BD, MI, RP and MWD did not differentiate between grazing systems, indicating a similar soil quality between integrated and non-integrated grazing systems , which might be related to time since the experiment establishment. Further research is required for integrated and non-integrated grazing systems, including assessments of long-term experiments and testing novel indicators of soil quality.
O aquecimento global, acentuado por ações antrópicas de emissão de gases de efeito estufa, tem como consequência as mudanças climáticas, que causam muitos transtornos ambientais para a humanidade. A atividade pecuária produz gases de efeito estufa na forma de metano (CH4) e óxido nitroso (N2O) principalmente, com tendência de aumento de emissão atrelado ao aumento da produção pecuária. A degradação de pastagens, o mais importante problema ambiental da pecuária, também pode contribuir para a emissão desses gases e pode levar à desertificação. Ações de mitigação dessas emissões podem amenizar o problema e devem ser observadas considerando-se o balanço de carbono dos sistemas de produção pecuários, onde, além da emissão de gases de efeito estufa, o sequestro de carbono é também considerado. Na pecuária, existe possibilidade de mitigação das emissões pela redução da emissão do CH4 e do N2O, entretanto, o maior potencial de mitigação das emissões está no sequestro de carbono devido à recuperação das pastagens. Apesar disso, grande ênfase é dada aos aspectos envolvendo a emissão de CH4 entérico pelos ruminantes e suas formas de mitigação. Também é importante ressaltar que a adoção das tecnologias que promovem a mitigação das emissões de gases de efeito estufa depende mais de questões econômicas do que da viabilidade técnica das ações de mitigação propostas. Global warming is intensified by greenhouse gases emissions from human activities, resulting in climate change and causing many environmental disorders for humanity. The livestock produces greenhouse gases such as methane (CH4) and nitrous oxide (N2O) mainly and the increasing in emissions is linked to increased livestock production. The degradation of pastures had been the most important issue of livestock contributing to the greenhouse gases emissions and leading the desertification. Mitigation actions can reduce these emissions and the carbon balance of livestock production systems, which also considerate carbon sequestration besides the emission of greenhouse gases. Mitigating emissions of CH4 and N2O are possible in livestock but the carbon sequestration that occurs during the recovery of pasture is the greatest potential for mitigating greenhouse. Nevertheless, great emphasis can be found in literature related to the aspects involving the issue of enteric methane by ruminants and its methods of mitigation. Importantly, the adoption of technologies that promote mitigation of greenhouse gases emissions is most dependent of economic issues than technical feasibility of the mitigation actions proposed. Keywords: livestock, desertification, degradation, methane, nitrous oxide.
The aim of the present study was to assess the effect of Eucalyptus trees in a silvopastoral system on the microclimate and the capacity of that to mitigate the effects of climate change on pasturelands. This study included an open pasture of Piatã palisadegrass and an adjacent pasture that contained both palisadegrass and East-to-West rows of Eucalyptus trees, with 15 m between rows, 2 m between trees within rows. The micrometeorological measurements were collected at several distances from the tree rows and in the open pasture. The silvopastoral system was associated with greater between-row shading when solar declination was high and greater near-tree shading when solar declination was around -22°. Both soil heat flux and temperature were influenced by solar radiation, wind speed, and the ability of tree canopies to reduce radiation losses. Wind speed was consistently lower in the silvopastoral system, owing to the windbreak effect of the Eucalyptus trees. The present study demonstrated that silvopastoral systems can be used to attenuate the effects of climate change, as trees can protect pastureland from intense solar radiation and wind, thereby reducing evapotranspiration and, consequently, improving soil water availability for the understory crop.
This study aimed to evaluate the production characteristics of pastures in integrated livestock production systems. For that, an experiment was carried out in São Carlos, SP, Brazil, from 2013 to 2015. Forage development, production and nutritive value were evaluated in five beef cattle production systems: extensive continuous stocking (Urochloa decumbens) = EXT; intensive = INT; crop-livestock = iCL; livestock-forest = iLF and crop-livestock-forest = iCLF. Rotational stocking pastures in INT, iCL, iLF and iCLF systems were established with Urochloa brizantha cv. BRS Piatã. In iCL and iCLF, pastures were renovated by resowing the grass simultaneously with corn. In iLF and iCLF, eucalyptus (Eucalyptus urograndis clone GG100) was planted in Apr 2011 in single rows with 15 × 2 m spacing. In the 2013/2014 crop season, INT, iCL, and iCLF pastures were more productive than in iLF and EXT. Shading increase in the 2014/2015 season reduced pasture production in iLF and iCLF, compared with INT and iCL, but increased crude protein content and digestibility. In the shaded systems, pasture production was affected by proximity to trees, mainly due to reductions in solar radiation transmission. The principal component analyses showed that forage accumulation and leaf area index were associated with the position in the middle of the inter-row, and nutritive value was associated with the position at 1.5 m from the trees. In iCLF, solar radiation transmission greater than 60 % maintained forage accumulation similar to iCL, while in iLF, it reduced forage accumulation, evidencing that pasture renovation minimized shading effects in these systems.
The aim of this study was to model the individual height and volume of eucalyptus wood in two integrated crop-livestock-forest systems (ICLF1 and ICLF2) in Campo Grande, a city in the state of Mato Grosso do Sul, Brazil. Classic nonlinear growth models were adjusted for height (Logistic, Gompertz, Richards, Weibull, Van Bertalanffy, Brody, Mitscherlich, and Chapman and Richards) and volume (Shumacher-hall nonlinear, Takata, Honner, Logistic, Gompertz, and Weibull) in two structural arrangements: ICLF1, with a spacing of 14 x 2 m and density of 357 trees ha-1 , and ICLF2, with a spacing of 22 x 2 m and density of 227 trees ha-1. Diameter at Breast Height (DBH) measurements were performed in 100% of trees, with measurements of the total height of some individuals and a rigorous scaling procedure in diameter classes. According to the calculated value of Student's t-test, there was no significant evidence that DBH and the average height of the trees were different between ICLF1 and ICLF2. Based on the Akaike information criterion (AIC), the corrected Akaike information criterion (AICC) and the Bayesian information criterion (BIC), the Richards model was selected to estimate heights and the Takata model was selected to estimate the volume.
Integrated crop-livestock-forestry systems are strategies to diversify production in the same area, aiming at higher sustainability. Corn is one of the most used crops in integrated systems due to its multiple uses on the farm. The objective of this study was to evaluate the effect of light restriction on morphological and productive characteristics of the forage components (corn for silage and pastures) in integrated livestock production systems. The experiment was carried out on Embrapa’s integrated systems in São Carlos, SP, Brazil, during two growing seasons. In the integrated crop-livestock (iCL) system corn was sown simultaneously with Piatã-grass. In the integrated crop-livestock- forestry (iCLF) system, besides corn and Piatã-grass, Eucalyptus urograndis trees were planted in single 15 × 2 m rows. Corn productivity and pasture yield and nutritive value were evaluated in iCL and iCLF systems. In iCLF, evaluations were made in four positions relative to the tree lines: 1.5, 3.75, 7.5, and 11.25 m. Photosynthetically active radiation (PAR) transmission by trees was also measured in the same positions. Results of the corn crop indicated that the position relative to the tree lines affected (P < 0.001) all morphological characteristics and production parameters. Production was not affected by position relative to the tree lines in the first year but was lower in the position closer to the trees in the second year. As an average of all positions evaluated in iCLF, corn DM production in the first agricultural year was 43.3% inferior compared to the second year (5266.1 vs. 9816.7 kg DM ha⁻¹). In iCL, the average corn DM production for the two years was 10082 kg DM ha⁻¹. For the corn, the relationship between PAR transmission and the relative yield (production in each position in iCLF divided by the production in iCL) was influenced by drought in the 2013/2014 growing season. Considering the results for the renovated pastures, position relative to the tree lines affected pasture height (P < 0.0001), specific leaf area (P < 0.0012), digestibility (P < 0.0085) and crude protein (P < 0.0001).
The degree to which pruning helps reestablish balance in agroforestry was assessed in a system established in Sao Carlos, Sao Paulo, Brazil, in 2008. Seven native tree species were planted at a density of 600 trees/ha in five strips of three rows each, and annual crops were cultivated in the 17-m crop strips between the tree strips. Competition was established after 35 months, decreasing the aboveground biomass production of corn planted close to the trees. An assessment of black oats in the dry season following tree pruning showed that the proximity of trees caused reductions in plant and panicle density, aboveground biomass production, number of grains per panicle and grain weight. Because pruning was not sufficient to maintain crop yields, tree thinning is recommended in order to minimize competition and restore conditions for adequate crop production.
Até a década de 1960, a pecuária de brasileira baseava-se em pastagens naturais, principalmente, em áreas de formações savânicas e campestres. A partir daí, ocorreu uma expansão em áreas com pastagens cultivadas, principalmente, nos biomas Cerrado e Floresta Amazônica, refletindo em aumento de produtividade, para suprir as crescentes demandas por produtos de origem animal, especialmente, carne e leite. O processo de estabelecimento das primeiras pastagens cultivadas nestes biomas, entretanto, ocorreu com a derrubada da vegetação nativa por meio do uso do fogo. Este processo permitiu o desenvolvimento de sistemas extensivos de produção pecuária, baseados na fertilidade natural, pelos altos teores de matéria orgânica do solo, e pelas cinzas provenientes da queima da vegetação nativa. Estes sistemas produtivos, meramente extrativistas, caracterizam-se pelo mínimo uso de insumos e tecnologias, apresentando, ao longo do tempo, baixos índices zootécnicos e contribuindo para a degradação dos recursos naturais. A perda gradual da capacidade produtiva destas pastagens, após alguns anos de sua implantação, processo conhecido como degradação das pastagens, tem sido uma constante nesses agroecossistemas, nos quais, segundo Martins et al. (1996), a produtividade de carne sofre uma redução da ordem de 6% ao ano. A partir da década de 1980 e, principalmente, na década de 1990 e mais recentemente, a renovação de pastagens degradadas e a abertura de novas áreas ocorreu com a introdução do braquiarão (Brachiaria brizantha cv. Marandu) e, em áreas restritas, por novas cultivares de P. maximum e de Andropogon gayanus. Até o final da década de 1990, estimativas realizadas pela Embrapa, na região do Cerrado, indicavam que mais de dois terços das pastagens cultivadas apresentavam algum grau de degradação, com capacidade de suporte inferior a 0,8 UA/ha/ano (Barcellos, 1996; Sano et al., 1999; Zimmer & Euclides, 2000). Nessas áreas, considerando-se somente a fase de engorda, a produtividade de carne encontrava-se em torno de 2 arrobas/ha/ano, enquanto que, em áreas de pastagens em bom estado de conservação, podia-se atingir, em média, 16 arrobas/ha/ano (Kichel et al., 1999). Já para a região da Amazônia brasileira, estimativas da década de 1990 indicavam que metade da área com pastagens cultivadas encontrava-se degradada ou em degradação (Serrão et al., 1993). Segundo Dias-Filho (2007), o estabelecimento incorreto e o manejo inadequado da pastagem já estabelecida têm sido apontados como os principais fatores de influência antrópica direta que contribuem no processo de degradação das pastagens. Pastagens degradadas ensejam baixa produtividade forrageira e diminuição da matéria orgânica do solo e, consequentemente, menor produtividade animal e taxa de desfrute, características que contribuem para aumentar a emissão de gases de efeito estufa por unidade de produto. Este cenário foi determinante para que, a partir da década de 2000, o Brasil sofresse forte pressão internacional, com barreiras não-tarifárias impostas à carne bovina brasileira. Entretanto, estimativas mais recentes, citadas por Macedo (2005), indicavam que a lotação das pastagens cultivadas do Cerrado aumentou, no período de 1995 a 2005, passando de 0,9 a 1,0 cabeça/ha para 1,15 a 1,20 cabeça/ha, sendo esse fato associado ao aumento da taxa de desfrute, de 12%, na década de 1970, para atuais 22%.
Para a próxima década, Ferraz (2008) prevê um cenário de redução das áreas de pastagens no Brasil, devido ao aumento nas demandas por lavouras para produção de grãos e de biocombustíveis, entretanto, com manutenção ou ligeiro aumento do rebanho. Esta tendência é justificada pelo maior uso de tecnologias e, consequentemente, maior produtividade das pastagens remanescentes, em decorrência da combinação de maior uso de insumos na manutenção das pastagens, da melhoria de técnicas de manejo e incremento da suplementação alimentar dos rebanhos, além de um aumento expressivo de sistemas de
integração lavoura-pecuária-floresta (iLPF). Assim, a partir de tecnologias já existentes e em desenvolvimento, que permitam uma melhoria na produtividade animal, incluindo a recuperação de pastagens, é possível contribuir para mitigação da emissão de gases de efeito estufa. Atualmente, o governo brasileiro instituiu, a partir de compromisso assumido na Conferência das Partes (COP-15), em 2009, um programa para diminuição voluntária das emissões de gases de efeito estufa do setor da agropecuária, denominado, Programa ABC (Agricultura de Baixo Carbono). Este programa disponibilizará crédito, dentre outros, para recuperação de 15 milhões de hectares com pastagens degradadas, até 2020 (Brasil, 2010), visando à melhoria da sustentabilidade da pecuária brasileira.
By combining crop, livestock and/or forestry activities in the same area, integrated systems (IS) can increase organic matter content in the soil – which favors biomass production and allows for higher livestock stocking rates in pasturelands. The implementation of IS is therefore seen as a promising strategy for sustainable agricultural intensification in Brazil, particularly in Mato Grosso state (MT). However, despite the benefits associated with IS and incentives offered by the federal government to stimulate their dissemination, little is known about these systems or the challenges to implement them, and only a limited number of farmers have adopted IS so far. This paper presents a comprehensive assessment of all IS identified in Mato Grosso by 2012/13, which were mapped and described in terms of their main technical and non-technical features. These findings were combined with farm survey data set to provide a detailed account of the various technologies currently being disseminated, their individual diffusion levels and potential adoption constraints. Results generated through qualitative and quantitative research methods give an overview of IS’ state of the art, reveal farmer perception of such technology and offer insights into the prospects for low-carbon agriculture in the region. The study’s major findings are that IS are present in more than 40 of the 141 municipalities of MT, and the vast majority (89%) involve only crop and livestock. Farmers have adopted three different crop–livestock configurations, depending on their production strategy. Cultural aspects play a major role in farmer decisions to adopt IS, credit provision has not been relevant for IS adoption, and a broader dissemination of IS may occur as land transitions continue.
This study compares the ability of several poplar (Populus spp.) stand parameters to predict photosynthetically active radiation (PAR) transmission through the overstorey canopy in a silvopastoral system. As an indirect measure of PAR transmission, diffuse non-intercepted radiation (DIFN) levels underneath fully foliated poplar stands were measured in two climatically contrasting regions of the North Island of New Zealand. The ability of several easily measured stand inventory parameters to predict understorey DIFN was then evaluated using regression analysis. Pasture net herbage accumulation (NHA) was also measured below the fully foliated trees and related to understorey DIFN. A directly inverse relationship between DIFN in the gap between tree crowns and stand canopy closure measured with a standard digital camera was found to be the simplest, most accurate and robust of the stand parameters examined. In comparison, there were site differences in the relationship for this understorey environment for all of the stand parameters based on individual tree metrics. Site differences in the relationship for DIFN directly underneath the tree-crowns were also apparent for both the stand parameters based on individual tree metrics and digital photographs. Inter-site variation in these relationships was attributed to unaccounted differences in stand leaf area. There was a strong straight-line relationship between DIFN and understorey pasture NHA.
Com a criação do Mecanismo de Desenvolvimento Limpo (MDL), foi gerado um amplo debate global sobre o potencial da silvicultura e da agrossilvicultura como atividades elegíveis para sequestro de carbono. O objetivo deste trabalho foi estimar o estoque de biomassa e carbono em um sistema silvipastoril misto com Eucalyptus grandis e Acacia mangium, implantado na Zona da Mata Mineira. O sistema apresenta uma densidade de árvores de 105 plantas por hectare, sendo 60 árvores de eucalipto e 45 árvores de acácia. Para tanto, primeiramente, foi feita a quantificação do volume do fuste das árvores aos 10 anos de idade, por meio do ajuste de equações alométricas e a quantificação da biomassa residual média da pastagem durante o período de 4 anos. Para o eucalipto, foi estimado um total de 24,8 Mg.ha-1 de biomassa e 11,17 Mg.ha-1 de carbono, para a acácia foi estimado um total de 6,94 Mg.ha-1 de biomassa e 3,12 Mg.ha-1 de carbono, totalizando 31,74 Mg.ha-1 de biomassa e 14,29 Mg.ha-1 de carbono. Para o componente pastagem, foi estimado um acúmulo de 1,28 Mg.ha-1 de biomassa e 0,58 Mg.ha-1 de carbono somente no resíduo do pastejo.
doi: 10.4336/2009.pfb.60.11
O modelo de Clutter (1963) é amplamente utilizado na predição do crescimento e produção de florestas plantadas no Brasil, especialmente eucalipto. Não obstante, esse modelo também é empregado em povoamentos submetidos a desbaste. A principal crítica enfrentada nesta última abordagem é a falta de flexibilidade. Os dados foram obtidos de um experimento de desbaste realizado em povoamentos de E. grandis x E. urophylla, no Norte da Bahia, em que se aplicaram desbastes de 20, 35 e 50% da área basal, eliminando-se as piores árvores. Utilizando os dados experimentais, buscou-se avaliar a proposta de modificação do modelo de Piennar e Shiver (1986), visando obter mais flexibilidade para captar tendências pré e pós-desbastes. Também, foi analisado o comportamento do modelo de Clutter (1963) na modelagem de povoamentos de eucalipto submetidos a desbaste no Norte da Bahia. A partir dos resultados, concluiu-se que o modelo proposto apresentou características estatísticas semelhantes ao modelo de Clutter, sem acrescentar a este maior flexibilidade. Além disso, observou-se que o modelo de Clutter, mesmo não diferenciando tendências de crescimento, pode ser usado sem prejuízo para simulação de desbaste.
Sustainability is an actual theme and very present in all discussion in the tropical agriculture world, including Brazil. This country experienced high taxes of development in agribusiness, increasing exportation trading, producing foods of better quality and raising incoming rates of farmers. However, two mains aspects call the attention in respect to sustainability: excessive soil preparation with monoculture of annual crops and pasture degradation. These situations have brought losses in crop and livestock yields, increased soil degradation and collapse of natural resources. Continuous cropping of monoculture accelerates attacks of insects and diseases, specially the ones related to soil interactions. Technologies such as minimum tillage, crop rotation and crop-livestock integration can alleviate these problems and drive agriculture to sustainability. Minimum tillage has increase to more than 60% of soil tillage usage in Brazil. Adoption of this system in large scale, covering more regions, with different clime and soil, is highly dependent of crops that produce high amounts of residues and straw for better soil coverage. Crop-livestock integrated systems (CLIS) have been cultivated with many crops, such as: soybeans, corn, pearl millet, sorghum, cotton, sunflower, etc. and especially perennial tropical grasses asBrachiaria spp, intercropped or not. CLIS can be one important alternative to pasture recuperation and improvement of annual crops. They increase straw to minimum tillage systems, improve soil chemical, physical and biological properties, and better use of equipments, farmers income, and jobs in rural area. This paper analyze the state of the art in CLIS research, later results, and bring some considerations for the near the future of CLIS in Brazil.
In 1996 we initiated a study to evaluate several techniques for measuring light under broadleaf canopies. Hourly average photosynthetic photon flux density and percent transmittance were measured 1 m above the ground at four points in each of three canopy densities created by a spacing experiment in a 35-year-old paper birch (Betula papyrifera Marsh.) dominated stand located near Prince George, B.C. At each point, fisheye photographs were taken and LAI-2000 plant canopy analyzer (LAI-2000), spherical densiometer, and competition index (Lorimer's index) measurements were made. Percent transmittance measurements on an overcast day (1-h average), transmittance measured over periods of 3 h or longer on a clear day, LAI-2000 diffuse noninterceptance measurements, and gap light index determined from fisheye photographs were strongly correlated with growing season percent transmittance (r2>= 0.96) as was competition index (r2 = 0.928). Concave spherical densiometer measurements and midday percent transmittance measurements on clear days were also well correlated with measured percent transmittance (r2>= 0.89). Estimates of understory light by the LITE model were strongly correlated with growing season percent transmittance. Correlations improved with increasing length of the period simulated (r2 = 0.755 for a point measurement on a clear day; r2 = 0.936 for an entire sunny day; and, r2 = 0.953 for the entire growing season). However, this version of the model underestimated percent transmittance in these spaced birch stands by 34-90%.
The ecological principles that define the competitive and complementary interactions among trees, crops, and fauna in agroforestry systems have received considerable research attention during the recent past. These principles have not yet, however, been adequately integrated and synthesized into an operational approach. This paper reviews the ecological and ecophysiological bases for interspecific interactions based on data from site-specific research and demonstration trials from temperate agroforestry systems, primarily from temperate North America. The review shows that information on ecological interactions in several temperate agroforestry systems is inadequate. It is recommended that the future research should focus on exploring new species and systems that have received little attention in the past. Priority research areas should include cultural practices and system designs to minimize in-terspecific competition and maximize environmental benefits such as improved water quality. Potential for genetic modification of components to increase productivity and reduce competition also needs to be explored. Process-oriented models may be used increasingly to predict resource-allocation patterns and possible benefits for a suite of site and species combinations.
With renewed interest in the use of ecologically-designed, sustainable agricultural systems for temperate regions of the world, agroforestry is being proposed as an alternative to intensive production of crops in monocultures. However, the knowledge-base for understanding and managing complex, multi-strata systems worldwide is limited, particularly so for temperate regions. We examined an alley cropping system in the midwestern US where maize (Zea mays L.) is grown in alleys between tree rows of either black walnut (Juglans nigra L.) or red oak (Quercus rubra L.). During a course of ten years, crop yields in rows adjacent to tree rows declined by 50% or more. With the experimental introduction of barriers to separate tree and crop root systems, yields in the rows near trees were equal to those of the center row (and monoculture). Irrespective of a high correlation between photosynthetically active radiation and net photosynthesis, shading did not have a major influence on crop yield. At this stage of system development (11 year old trees), influence of incident PAR on crop yield seems to be minimal. Subsequent papers in this series examine the sharing of belowground resources between trees and crops to quantify the competitive interactions that impact crop yields and their implications for economic return to the farmer.
In 1987, the University of Guelph established a large tree-based intercropping system on 30 ha of prime agricultural land in southern Ontario, Canada. The purpose was to investigate various aspects of intercropping trees with prime agricultural crops. In this study, objectives were to investigate tree competitive effects (i.e., shading and competition for soil moisture) on under-story crop net assimilation (NA), growth, and yield. The effects of tree competition on corn (C4 plant) and soybean (C3 plant) photosynthesis and productivity in the intercropped system were studied during the 1997 and 1998 growing seasons. Corn and soybeans were intercropped with hybrid poplar (clone-DN-177) and silver maple (Acer sacharrinum) at a within-row spacing of 6 m and between-row spacing of 12.5 or 15 m. Trees were absent from control rows. Tree rows were oriented approximately north and south. Twelve crop locations were sampled around each tree. These were at 2 and 6 m east and west of the tree, located along a primary axis running through the tree trunk and perpendicular to the tree row, and at 2 m north and south of each location along the primary axis. Net assimilation and plant water deficit measurements were made three times daily (morning, noon, afternoon) on sampling days in July. Generally, tree competition significantly reduced photosynthetic radiation (PAR), net assimilation (NA), and growth and yield of individual soybean or corn plants growing nearer (2 m) to tree rows in both years and soil moisture in 1998. NA was highly correlated with growth and yield of both crops. These correlations were higher for corn than soybeans in both years, with corn, rather than soybeans being more adversely impacted by tree shading. In 1997, poplar, rather than maple, had the greatest competitive effect on NA. In 1997, the lowest plant water deficits, for soybeans and for corn, were observed for the maple treatment. Nonetheless, in both years, daily plant water deficits were non-significantly and poorly correlated with NA and growth and yield of both crops. However, soil moisture (5 and 15 cm depth) was significantly correlated with soybeans yield in 1998. Possible remediation strategies are discussed to reduce tree competitive interactions on agricultural crops.
The intensive land use invariably has several negative effects on the environment and crop production if conservative practices are not adopted. Reduction in soil organic matter (SOM) quantity means gas emission (mainly CO2, CH4, N2O) to the atmosphere and increased global warming. Soil sustainability is also affected, since remaining SOM quality changes. Alterations can be verified, for example, by soil desegregation and changes in structure. The consequences are erosion, reduction in nutrient availability for the plants and lower water retention capacity. These and other factors reflect negatively on crop productivity and sustainability of the soil-plant-atmosphere system. Conversely, adoption of "best management practices", such as conservation tillage, can partly reverse the process they are aimed at increasing the input of organic matter to the soil and/or decreasing the rates at which soil organic matter decomposes.
The objectives of this work were to evaluate the effects of trees arranged in rows on yield and nutritional
characteristics of Urochloa decumbens and to identify the average distance in which there is a better use of
moderate shading in an agrisilvipasture system. The treatments consisted of distances from measure points to tree
rows (0, 3, 6, 9, 12 and 15 m) and were distributed in randomized blocks, with four replicates. The tiller density,
forage mass, forage accumulation rate and chemical composition of pasture were evaluated. The tiller density,
forage mass and rates of forage accumulation increased with the distance from tree rows, reaching the highest
values of 392 tillers m‑2, 1,347 kg ha‑1 and 30.1 kg ha‑1 per day, respectively, at 9.1, 10.4 and 8.8 m of distance. The
contents of the neutral detergent fiber did not vary with distance, while the acid detergent fiber and lignin content
varied, but without a clear pattern of response. The crude protein contents reduced quadratically with distance
from tree rows and had the highest values under trees (9.8%) and the lowest at 13.5 m of distance (6.5%). The site
of pasture, between 7 and 10 m of distance from the tree rows showed the highest benefits of moderate shading
on pasture traits.
Data from six aspen stands in northeastern British Columbia ranging in age from 12 to 40 years were used to examine relationships between understorey light levels and stand attributes (basal area, stand density, and age). Sample points were selected in each stand to characterize the observed range in tree density and size. Fractional transmittance of light (DIFN) was measured at each sample point using a LAI-2000 Plant Canopy Analyzer and a circular plot 3.99 m or 5.64 m in radius was established for density and basal area determination.Results indicated that data from the six stands could be pooled into a single model describing the relationship between understorey light and basal area. Light levels below 40% are found when basal area of aspen in these stands exceeds 14 m2/ha and light levels below 60% are found when basal area of aspen exceeds 8 m2/ha. The potential implications of these light levels to growth of understorey spruce are discussed.A diagrammatic representation of light-density–diameter relationships is presented that could provide a useful tool for management decisions in young mixedwood stands in northeastern British Columbia.
This study aimed at evaluating the effect of different thinning intensities in the dendrometric and technological characteristics of 14 years-old Eucalyptus grandis W. Hill ex Maiden wood sited in the northern coast of Rio Grande do Sul. Randomized blocks experiment, with four treatments (T1 = 1638 trees/ha; T2 = 1150 trees/ha; T4 = 589 trees/ha and T8 = 192 trees/ha) and four repetitions was analyzed. The trees were selected on the basis of the dominant and average diameter of each treatment. After cutting down, trees were measured and the volume was determined by the Smalian method, disks were taken at the base 0, 25, 50, 75 and 100% of the commercial height, and at the DBH (diameter at breast height), for basic density, dry mass and radial shrinkage determination. In relation to the dendrometric characteristics, results indicate that the application of more severe thinning caused significant gain in diameter at breast height, height and volume in average trees, not influencing the dominant ones. Concerning the technological characteristics, results indicate that the basic density of the average trees was influenced by thinning; however, without presenting clear trend regarding the intensity of the intervention. The production of dry mass of the average trees increased with the thinning intensity and did not affect the production of the dominant trees. The radial shrinkage of the dominant and average trees grew up in the pith-to-bark direction, not being modified by thinning intensity. Results allow concluding that the silvicultural interventions applied in the forest influence wood quality.
The goal of this study was to evaluate the effects of thinning eucalyptus trees on yield and nutritive value of corn for silage and palisadegrass in a crop–livestock–forest integrated system and to evaluate the total aboveground biomass yield in systems with and without trees. Plant variables, as well as the incidence of photosynthetically active radiation (PAR) and soil moisture, were evaluated between October 2016 and March 2018 in São Carlos, Brazil, in a crop–livestock–forest and a crop–livestock system. In the crop–livestock–forest system, eucalyptus trees ( Eucalyptus urograndis clone GG100) were planted in April 2011, in single rows, with 15 × 2 m spacing. In 2016, the trees were thinned, and the spacing was changed to 15 × 4 m. The treatments comprised measurements at 0.00, 3.75, 7.50, and 11.25 m from the trees of the North row in the integrated crop–livestock–forest (iCLF) system and integrated crop–livestock (iCL) system. Palisadegrass ( Urochloa brizantha ) was sown after harvesting the corn. Corn yields were similar between treatments, with an average of 13.6 Mg ha ⁻¹ . Corn for silage presented a higher percentage of grain in total biomass in the crop–livestock–forest positions (41.4 and 42.1%) than in the crop–livestock system (35.6%). No differences in forage accumulation were observed. Crude protein content in corn for silage and palisadegrass was higher in the crop–livestock–forest treatments than in the crop–livestock system. Such results indicate that thinning was favorable to production in the crop–livestock–forest system. Total aboveground biomass yield was higher in the iCLF system, indicating better land use for this type of integrated system.
A newly developed indirect method for lignin, utilizing permanganate, permits the determination of cellulose and insoluble ash in the same sample. The new permanganate lignin method is intended as an alternative procedure to the 72% sulfuric acid method over which it offers definite advantages as well as certain disadvantages. Choice of methods will depend upon the materials analyzed and the purpose for which the values are to be used.
The understanding of plant morphological and physiological
responses to shading can contribute to developing sustainable
silvopastoral systems (SPS). Our objective was to evaluate
the shading effect on herbage accumulation (HA), plant-part
composition, physiology, and canopy structural characteristics
of Marandu palisadegrass {Urochloa brizantha (Hochst. ex A.
Rich.) R.D. Webster [syn. Brachiaria brizantha (Hochst. ex
A. Rich.) Stapf]} under intermittent defoliation in a SPS with
Eucalyptus urograndis (hybrid of Eucalyptus grandis W. Hill ex
Maiden and Eucalyptus urophylla S.T. Blake) in Sinop, Mato
Grosso, Brazil. The experimental design was a randomized complete
block arranged under a strip-split-plot, where the plots
were allocated to four distances from the Eucalyptus grove (3,
6, 10, and 15-m) in the SPS, on both faces (north and south),
with four replications. The evaluations were done during two
summer rainy seasons (RS1 and RS2) and one dry season (DS).
The herbage accumulation (HA) in RS1 (4290 kg DM ha–1)
was 51% greater than in RS2. The greatest canopy height, light
interception, and leaf area index (LAI) values were measured
during RS1 (25 cm, 91%, and 3.5 cm2 cm–2, respectively). Leaf
photosynthesis rate was less at the 3-m distance (12.5 μmol CO2
m–2 s–1) than at other distances (17.3 μmol CO2 m–2 s–1). We
conclude that Marandu palisadegrass has the ability to physiologically
adapt to shaded environments, although the dynamics
along the whole tree growing cycle needs to be considered so
that grass productivity can be sustained in the long-term.
This study aimed to assess solar radiation transmission and animal thermal comfort indexes in two silvopastoral systems established with different tree arrangements in a tropical region. This study was conducted between 2014 and 2017 in two silvopastoral systems, one composed by an established Urochloa (syn. Brachiaria) decumbens pasture with Brazilian native trees planted in triple rows spaced 17 m apart, and another by an established Urochloa (syn. Brachiaria) brizantha (Hochst ex A. Rich.) Stapf ‘BRS Piatã’ pasture with Eucalyptus urograndis (clone GG100) trees arranged in single rows spaced 15 m apart. In these systems and in a full-sun pasture, photosynthetically active radiation transmission, air temperature, relative humidity, black globe temperature, and wind speed were measured. These variables were used to calculate black globe temperature and humidity index (BGHI) and radiant thermal load (RTL). Higher animal thermal comfort was observed in the silvopastoral systems due to changes in the microclimate induced by the trees; notably, a decrease in solar radiation transmission. Fewer hours of potential animal thermal stress (BGHI>79) were observed in the silvopastoral systems than under the full-sun conditions, with differences up to 3 h per day. The silvopastoral systems presented lower radiant thermal load than the full-sun pasture with differences up to 22% achieved. The assessed silvopastoral systems may help livestock adapt to climate change, since they achieved the limit of BGHI considered to cause stress to animals following an increase of 2.2 °C in air temperature, compared with full-sun pastures.
The loss of productive capacity of pastures has a direct impact on livestock productivity and there is an inefficient use of natural resources. In this scenario, a production strategy that can reverse this degradation is the use of silvopastoral systems. This study aimed to evaluate the animal performance associated with the Piatã grass traits under open pasture and two silvopastoral arrangements in the Brazilian Cerrado. The forage was Brachiaria brizantha cv. BRS Piatã and the tree species was the Eucalyptus urograndis (Eucalyptus grandis x E. urophylla) planted in the North-South direction in the treatments: forage grown in treeless area (control); forage grown in eucalyptus understory with 22 m spacing between rows (SSP22); forage grown in eucalyptus understory with 12 m spacing between rows (SSP12). There was a higher availability of forage dry mass of Piatã grass in the treeless treatment in the rainy and dry seasons, and treatment SSP22 was superior to SSP12 in the rainy season. SSP12 and SSP22 pasture presented the highest content of crude protein and the lowest forage density. The leaf/stem ratio and in vitro dry matter digestibility were higher in control compared to SSP12. Cell wall components were affected by the season, but not by the treatments. The stocking rate was higher in the treeless treatment and the average daily gain of animals did not differ between treatments. The live weight gain per area (hectare) was higher in SSP22 compared to SSP12 and both were lower than the control. Chemical and structural characteristics of Piatã grass were affected by silvopastoral systems, which directly influenced animal performance. If livestock production is the only goal, spacing between tree rows not less than 22 m should be prioritized under silvopastoral system with eucalyptus trees planted in the North-South direction.
Integrated Systems (IS) have been identified as an efficient land-management strategy for
restoring degraded areas worldwide, increasing crops and beef yields and providing technical
potential for carbon (C) sequestration in soil and trees as an option for offsetting CH4 and N2O
emissions from cattle production. The aim of our study is to estimate the greenhouse gas (GHG)
balance and the C footprint of beef cattle (fattening cycle) in three contrasting production
scenarios on the Brachiaria pasture in Brazil—1) degraded pasture (DP), 2) managed pasture
(MP), and 3) the crop-livestock-forest integrated system (CLFIS)—presenting new alternatives
of land use as a GHG mitigation strategy. Area-scaled total GHG emissions were highest in MP
(84,541 kg CO2eq ha-1), followed by CLFIS (64,519 kg CO2eq ha-1) and DP (8,004 kg CO2eq
ha-1) over a 10-yr period. Our results note that the highest C footprint of beef cattle was in the
DP, 18.5 kg CO2eq per kg LW (live weight), followed by 12.6 kg CO2eq per kg LW in the CLFIS
and 9.4 kg CO2eq per kg LW in the MP, without taking into account the technical potential for C
sequestration in MP (soil C) and CLFIS (soil and Eucalyptus C). Considering the potential for
soil C sequestration in the MP and CLFIS, the C footprint of beef cattle could be reduced to 7.6
and -28.1 kg CO2eq per kg LW in the MP and CLFIS, respectively. The conversion of the
degraded pasture to a well-managed pasture and the introduction of CLFIS can reduce their
associated GHG emissions in terms of kg CO2eq emitted per kg of cattle LW produced,
increasing the production of meat, grains and timber. This reduction is primarily due to pasture
improvement and increases in cattle yields and the provision of technical potential for C sinks in
soil and biomass to offset cattle-related emissions.
Information is needed on microclimatic differences present in different landscapes, such as open-pasture versus silvopasture, in the Southeast USA. This research tested a hypothesis that microclimatic conditions in mature-pine silvopasture would be milder compared to open-pasture. The research objective was to quantify microclimatic differences between mature-pine silvopasture and open pasture. The research was conducted in a loblolly-pine (Pinus taeda L.)-bahiagrass (Paspalum notatum Flugge) silvopasture and an open bahiagrass pasture, 5-ha each, in Chipley, Florida. Microclimatic parameters (air temperature, soil temperature at 5- and 10-cm depths, wind speed, gust speed, wind direction, humidity, dew point, rainfall, soil-moisture content, total solar radiation, and photosynthetically active radiation) were collected from November 2005 to January 2008 using HOBO© weather stations located in each pasture type. Data were analyzed to determine overall, as well as seasonal, monthly, and diurnal differences between pasture types. Evapotranspiration was calculated from air temperature, wind speed, relative humidity, and total solar radiation. The overall average values for all microclimatic parameters were lower in silvopasture compared to open-pasture. Seasonal, monthly, and diurnal differences between pasture types were also detected for several parameters. These results indicate that milder microclimatic conditions occur in silvopasture versus open-pasture on the Coastal Plain of the Southeast USA.
To derive optimal benefits from intercropping timber, farmers should make important initial decisions on tree species and
planting density with a good understanding of their tradeoffs. Complex and data-intensive models used by researchers should
be supplemented with simpler models based on easily measured parameters and easily understood competition functions. In experiments
in the Philippine uplands, growth parameters of three popular farm-forestry species (Eucalyptus deglupta, E. torelliana, and Paraserianthes falcataria) were measured, along with intercropped and non-intercropped yields of maize and vegetables. The commonly used forestry parameter
of stand basal area had a significant negative correlation with intercrop yields (as a percentage of non-intercropped yields).
The slope of the regression line differed between species; in this study, percent yield loss per unit stem basal area growth
was in the order E. deglupta > E. torelliana > P. falcataria. The relationship between stand basal area and intercrop-yield decline was tested on an independent data set from China.
Intercrop yields had significant negative correlations with stand basal area of Paulownia elongata. We propose that adaptive tree-screening trials evaluate competitiveness in addition to evaluating growth and mortality.
Stand basal area may be better suited to this task than more mechanistic indices such as leaf-area index as it is easy to
measure, calculate, and understand, and it may serve as a better index of total (aboveground + belowground) competition. Basal
area is also directly related to tree volume, and allows farmers to more easily evaluate the economic tradeoffs between tree
growth and intercrop-yield declines.
Soil moisture content from 0 to 2m depth was monitored under 2–6year old radiata pine (Pinus radiata) with three understoreys of bare ground, lucerne (Medicago sativa) and ryegrass/clover (Lolium perenne/Trifolium spp.) and under adjacent open-grown lucerne and ryegrass/clover pastures. By the fifth year soil moisture depletion/recharge
pattern under the trees alone was similar to that under open pasture and under trees with pasture understoreys. Maximum plant
available moisture storage was 207–223mm in the top meter of this Templeton silt loam soil but only 69–104mm at 1–2m depth
where coarse textures often predominated. Lucerne reduced soil moisture content (SMC) to lower levels during drier summers
and extracted more water from 1 to 2m depth than ryegrass/clover. Evapotranspiration (ET) during early summer when soil moisture
was high was close to the Penman potential evapotranspiration (E
p
), but the difference increased when SMC in the top meter dropped below 200mm. The silvopasture treatments had higher ET
in winter than pasture alone but this was still less than E
p
. Soil moisture deficits (SMD) at the end of each summer were sufficiently large to require slightly higher than normal winter
rainfall and ET<E
p
to recharge the soil to field capacity before the next summer. The soil moisture results, taken together with root and growth
data, suggest that trees and understorey pastures are complementary in the first three or four growing seasons but this balance
subsequently declines in favor of the pine trees. Management options, to extend the period that understorey pastures are productive,
include reducing tree stockings, more vigorous pruning, using competitive understoreys and changing from pines to deciduous
trees. Research on new silvopastoral combinations is suggested.
Pastures store over 90% of their carbon and nitrogen below-ground as soil organic matter. In contrast, temperate conifer forests
often store large amounts of organic matter above-ground in woody plant tissue and fibrous litter. Silvopastures, which combine
managed pastures with forest trees, should accrete more carbon and nitrogen than pastures or timber plantations because they
may produce more total annual biomass and have both forest and grassland nutrient cycling patterns active. This hypothesis
was investigated by conducting carbon and nitrogen inventories on three replications of 11 year-old Douglas-fir (Pseudotsuga menziesii)/perennial ryegrass (Lolium perenne)/subclover (Trifolium subterraneum) agroforests, ryegrasss/subclover pastures, and Douglas-fir timber plantations near Corvallis, Oregon in August 2000. Over
the 11 years since planting, agroforests accumulated approximately 740 kg ha–1 year –1 more C than forests and 520 kg ha–1 year–1 more C than pastures. Agroforests stored approximately 12% of C and 2% of N aboveground compared to 9% of C and 1% of N above
ground in plantations and less than 1% of N and C aboveground in pastures. Total N content of agroforests and pastures, both
of which included a nitrogen-fixing legume, were approximately 530 and 1200 kg ha–1 greater than plantations, respectively. These results support the proposition that agroforests, such as silvopastures, may
be more efficient at accreting C than plantations or pasture monocultures. However, pastures may accrete more N than agroforests
or plantations. This apparent separation of response in obviously interrelated agroecosystem processes, points out the difficulty
in using forest plantation or pasture research results to predict outcomes for mixed systems such as agroforests.
Understanding the effect of canopy structure on the understory light environment is useful in the design of silvicultural strategies that facilitate sustainable tree recruitment. To address this need, a study was designed to quantify the relationship between forest structure and light along a gradient of 50–100% canopy cover. The gradient was created by applying 1 of 4 midstory removal treatments to each of fifty 0.05 ha plots located within a mixed-hardwood riparian forest corridor. The light environment was directly quantified with a linear ceptometer and regression analysis was used to examine the relationship between photosynthetically active radiation (PAR) and various metrics of vertical and horizontal structure. Vertical sighting tube estimates of canopy cover (R2 = 0.73), light estimates derived from hemispherical photography (R2 = 0.70), and spherical densiometer estimates of canopy closure (R2 = 0.68) were the best single predictors of understory light transmittance. Including top height and tree density improved the fit of canopy cover based models (R2 = 0.80). Canopy closure estimates derived from hemispherical photography generally showed a weaker relationship with PAR than other measures of stand structure. Further, the strength of this relationship depended upon photo analysis angle. In general, the vertical component of stand structure seems to influence light transmittance through the forest canopy. This vertical complexity must be addressed when evaluating structure–light relations.
Changes in land use can result in either sources or sinks of atmospheric carbon (C), depending on management practices. In Brazil, significant changes in land use result from the conversion of native vegetation to pasture and agriculture, conversion of pasture to agriculture and, more recently, the conversion of pasture and agriculture to integrated crop-livestock systems (ICL). The ICL system proposes a diversity of activities that include the strategic incorporation of pastures to agriculture so as to benefit both. In agricultural areas, for example, the implementation of ICL requires the production of quality forage for animals between crops as well as the production of straw to facilitate the sustainability of the no-tillage (NT) management system. The objective of this study was to evaluate the modifications in soil C stocks resulting from the main processes involved in the changes of land use in Amazonia and Cerrado biomes. For comparison purposes, areas under native vegetation, pastures, crop succession and ICL under different edapho-climatic conditions in Amazonia and Cerrado biomes were evaluated. This study demonstrated that the conversion of native vegetation to pasture can cause the soil to function either as a source or a sink of atmospheric CO2, depending on the land management applied. Non-degraded pasture under fertile soil showed a mean accumulation rate of 0.46 g ha⁻¹ year⁻¹. Carbon losses from pastures implemented in naturally low fertile soil ranged from 0.15 to 1.53 Mg ha⁻¹ year⁻¹, respectively, for non-degraded and degraded pasture. The conversion of native vegetation to agriculture in areas under the ICL system, even when cultivated under NT, resulted in C losses of 1.31 in six years and of 0.69 Mg ha⁻¹ in 21 years. The conversion of a non-degraded pasture to cropland (soybean/sorghum) released, in average, 1.44 Mg of C ha⁻¹year⁻¹to the atmosphere.
On productive sites, young paper birch (Betula papyrifera Marsh.) outgrows most of the conifers with which it is associated. Due to its dominant position in the canopy, and the potentially high densities of birch regeneration found on some sites, its presence may lead to a reduction in the amount of light reaching subordinate conifers. To evaluate the potential use of stand attributes for estimating competition for light and understory light levels, we measured fractional transmittance of light (DIFN1) using Licor LAI-2000 Plant Canopy Analyzers, at a height of 1 m under the canopies of nine 10–40-year-old paper birch stands in southern interior BC. Various measures of broadleaf and conifer abundance were made at each of the 55 sample points where light measurements were taken. Vertical light gradients were also measured to a height of 8 m within birch canopies at four of the nine sites.Regression models were developed to predict understory light availability from broadleaf and conifer abundance. The models that best-fit the data were based on broadleaf basal area (BAb), and included either conifer cover (Cc) (R2=0.83) or conifer basal area (BAc) (R2=0.80). Broadleaf density (TPHb) alone was a poor predictor of understory light, but in combination with broadleaf quadratic mean diameter (QMDb) or height of the tallest broadleaf (HTb) the models improved (R2>0.85). Light availability increased rapidly with relative height in birch canopies, especially where transmittance to the understory was low; at 35% of the height from live crown base to top of the canopy (relative height of 0.35), approximately 80% full light was available.A diagrammatic representation of the relationship between DIFN1, QMDb and TPHb is presented as a potential tool for the development of stand-tending prescriptions. DIFN1, BAb and TPHb were all highly variable across individual sites, indicating that the models should be applied at the microsite level.
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Dube, F., Couto, L., Silva, M.L., Leite, H.G., García, R., Araújo, G.A.A., 2002. A simulation
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Integração lavourapecuária (ILPF), sistemas agroflora (SAFs)
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