► Most eucalypt plantations are managed in regions with high environmental stresses. ► Clonal plantations with interspecific hybrids strongly contributed to improve site-genotype adaptations. ► ...Continuous gains in productivity of eucalypt plantations have been obtained in Brazil. ► There are a number of risks associated with intensive, high yielding plantations. ► Integration of breeding and silviculture are imperative to sustain productivity.
Organized forestry in Brazil began in the late 1960s, stimulated by a government policy which subsidized afforestation programs from 1967 to 1989 to develop an internationally-competitive wood-based industry, managed by the private sector. Currently, planted forests in Brazil total about 6.9million ha, from which 4.9million ha is planted with eucalypt (around 25% of world plantation), 1.6million ha with pine, and 0.42Mha with other species. Roundwood consumption of forest plantations totaled 170.1millionm3 in 2011, eucalypt plantation accounted for 80.6% of this total.
Most eucalypt plantations are managed in short rotations (6–8years) and are established in regions with water, nutritional and frost stresses of low to high degrees. The mean annual increment is 40m3ha−1year−1 roundwood, ranging from 25 to 60m3ha−1year−1 depending on the level of environmental stress. Improving natural resources use efficiency by breeding and matching genotypes to sites and using appropriate site management practices is a key challenge to sustain or increase productivity.
The wide range of eucalypt species and hybrids with different climatic and edaphic suitability associated with the easy propagation by seeds and cloning allow the adaptation of plantations to various tropical and subtropical regions in Brazil. The possibility of using eucalypt wood in a range of purposes has led large and small enterprises to establish eucalypt forests for multiple uses. The desirable characteristics in association with the accumulated knowledge on eucalypt silviculture encourage the use of this genus in most plantations. The most important factors in the selective process for a genotype are wood characteristics, productivity level, susceptibility to pests and diseases, drought tolerance, especially in tropical regions (frost free), and frost tolerance in subtropical regions (mostly without water deficit). In regions with pronounced seasonality and moderate to long drought periods, the planting of hybrid genotypes predominates, propagated by cloning. Under subtropical conditions, the planting of single species predominates, propagated by seed. Clonal plantations with interspecific hybrids have been fundamental for eucalypt adaptation in regions under water and nutritional stresses. Given the rapid advances in eucalypt breeding, regarding adaptation to water stress and resistance to diseases and pests, and the adoption of clonal propagation techniques, genotypes are rapidly becoming obsolete and are replaced by more productive ones after harvesting. Thus, the replanting of crops has become a common procedure after the second half of the 1990s in Brazil.
This paper describes the basic requirements for integrating genetic and silvicultural strategies to minimize abiotic and biotic constraints in eucalypt plantations.
The combination effects of nitrogen (N) fertilizer and planting density on maize yield, N use efficiency and the characteristics of canopy radiation capture and radiation use efficiency are not well ...documented in the Huanghuaihai Plain region in China. A 2-year field experiment was conducted from 2017 to 2018 in a split plot design with two N levels (240 and 204 kg N ha
) applied to main plots and three plant densities (67,500, 77,625 and 87,750 plants ha
) allocated to sub plots. Our results show that a 30% greater plant density combined with a 15% lower N rate (basal N) enhanced N partial factor productivity (NPFP) by 24.7% and maize grain yield by 6.6% compared with those of the conventional high N rate combined with a low density planting management practice. The yield increase was mainly attributed to significantly increased kernel numbers and biomass. The increased intercepted photosynthetically active radiation (IPAR) was the primary factor responsible for the high productivity of maize at increased planting density under reduced N conditions. The results indicate that increase planting density with reduced basal N application might benefit maize cropping for achieving high yields and sustainable development of agriculture.
Several initiatives have been proposed to mitigate forest loss and climate change through tree planting as well as maintaining and restoring forest ecosystems. These initiatives have both inspired ...and been inspired by global assessments of tree and forest attributes and their contributions to offset carbon dioxide (CO₂) emissions. Here we use data from more than 130,000 national forest inventory plots to describe the contribution of nearly 1.4 trillion trees on forestland in the conterminous United States to mitigate CO₂ emissions and the potential to enhance carbon sequestration capacity on productive forestland. Forests and harvested wood products uptake the equivalent of more than 14% of economy-wide CO₂ emissions in the United States annually, and there is potential to increase carbon sequestration capacity by ∼20% (−187.7 million metric tons MMT CO₂ ±9.1 MMT CO₂) per year by fully stocking all understocked productive forestland. However, there are challenges and opportunities to be considered with tree planting. We provide context and estimates from the United States to inform assessments of the potential contributions of forests in climate change mitigation associated with tree planting.
1. Developing restoration strategies that accelerate natural successional processes and are resource-efficient is critical to facilitating tropical forest recovery across millions of hectares of ...deforested lands in the tropics. 2. We compared tree recruitment after a decade in three restoration treatments (natural regeneration, applied nucleation/island tree planting and plantation) and nearby reference forest in the premontane rain forest zone in southern Costa Rica. The study was replicated at 13 sites with a range of surrounding forest cover, enabling us to evaluate the relative influence of local restoration treatments and landscape forest cover on tree recruitment. 3. Density of small-seeded (<5 mm), animal-dispersed recruits was lower in natural regeneration than in applied nucleation, plantation or reference forest plots. Species richness, species density and density of medium (5-10 mm)- and large (>10 mm)-seeded, animal-dispersed recruits were greatest in reference forest, intermediate in applied nucleation and plantation and lowest in natural regeneration plots. 4. Recruit composition differed substantially between reference forest and all restoration treatments. In general, plantation recruit composition was more similar to reference forests and natural regeneration least similar; however, there was high within-treatment variation. 5. Models suggested weak support for the effect of surrounding forest cover on tropical tree recruit density and composition, as compared to restoration treatment and site conditions (e.g. elevation), in this intermediate forest cover landscape. 6. Synthesis and applications. Applied nucleation appears to be a cost-effective strategy as compared to plantation-style planting to accelerate tropical forest recovery regardless of the amount of forest cover immediately adjacent to the site. However, even with active restoration interventions, forest recovery is a multidecade process that proceeds at highly variable rates.
Summary
Improving yield is a primary mission for cotton (Gossypium hirsutum) breeders; development of cultivars with suitable architecture for high planting density (HPDA) can increase yield per unit ...area.
We characterized a natural cotton mutant, AiSheng98 (AS98), which exhibits shorter height, shorter branch length, and more acute branch angle than wild‐type.
A copy number variant at the HPDA locus on Chromosome D12 (HPDA‐D12), encoding a dehydration‐responsive element‐binding (DREB) transcription factor, GhDREB1B, strongly affects plant architecture in the AS98 mutant. We found an association between a tandem duplication of a c. 13.5 kb segment in HPDA‐D12 and elevated GhDREB1B expression resulting in the AS98 mutant phenotype. GhDREB1B overexpression confers a significant decrease in plant height and branch length, and reduced branch angle.
Our results suggest that fine‐tuning GhDREB1B expression may be a viable engineering strategy for modification of plant architecture favorable to high planting density in cotton.
Matching of maize growth with solar radiation is of great importance for achieving high yield. We conducted experiments using different maize cultivars and planting densities under different solar ...radiations during grain filling to quantitatively analyze the relationships among these factors. We found that a decrease in solar radiation after silking caused a drop in maize grain yield and biomass, with lower solar radiation intensities leading to worse grain yields and biomass. Cultivar ZD958 was more sensitive to solar radiation changes than cultivar XY335; slight decreases in solar radiation (i.e., 15% shading) caused significant declines in ZD958 grain yield. When total solar radiation during grain filling was less than 486.9 MJ m
for XY335 and less than 510.9 MJ m
for ZD958, the two cultivars demonstrated high yields at lower planting density of 7.5 × 10
plants ha
; average yields were 13.36 and 11.09 Mg ha
, respectively. When radiation intensities were higher than 549.5 MJ m
for XY335 and higher than 605.8 MJ m
for ZD958, yields were higher at a higher planting density of 12 × 10
plants ha
, with average yields of 20.58 Mg ha
for XY335 and 19.65 Mg ha
for ZD958.
To assemble a data set of global crop planting and harvesting dates for 19 major crops, explore spatial relationships between planting date and climate for two of them, and compare our analysis with ...a review of the literature on factors that drive decisions on planting dates. Global. We digitized and georeferenced existing data on crop planting and harvesting dates from six sources. We then examined relationships between planting dates and temperature, precipitation and potential evapotranspiration using 30-year average climatologies from the Climatic Research Unit, University of East Anglia (CRU CL 2.0). We present global planting date patterns for maize, spring wheat and winter wheat (our full, publicly available data set contains planting and harvesting dates for 19 major crops). Maize planting in the northern mid-latitudes generally occurs in April and May. Daily average air temperatures are usually c. 12-17 °C at the time of maize planting in these regions, although soil moisture often determines planting date more directly than does temperature. Maize planting dates vary more widely in tropical regions. Spring wheat is usually planted at cooler temperatures than maize, between c. 8 and 14 °C in temperate regions. Winter wheat is generally planted in September and October in the northern mid-latitudes. In temperate regions, spatial patterns of maize and spring wheat planting dates can be predicted reasonably well by assuming a fixed temperature at planting. However, planting dates in lower latitudes and planting dates of winter wheat are more difficult to predict from climate alone. In part this is because planting dates may be chosen to ensure a favourable climate during a critical growth stage, such as flowering, rather than to ensure an optimal climate early in the crop's growth. The lack of predictability is also due to the pervasive influence of technological and socio-economic factors on planting dates.
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