Converting Brazil's pastures to cropland: An alternative way to meet sugarcane demand and to spare forestlands

Brazil seeks to rapidly increase its agricultural production to meet future demands, especially for sugarcane, which is an agricultural commodity and a biofuel source. In this paper, we explore how to achieve this increase without compromising existing forestlands. We propose that it is possible to substantially expand sugarcane production in Brazil while avoiding further environmental losses and the indirect land use changes often associated with them, such as deforestation. This task could be accomplished by converting existing pasturelands with agricultural potential into cropland. A great deal of pastureland exists in Brazil. Thus, we addressed the following questions in this study: (1) where are the most suitable pasturelands for sugarcane located geographically and (2) what potential do these pasturelands have for sugarcane production regarding their physical suitability and other significant factors, such as infrastructure availability and socioeconomic factors. We conducted a land suitability analysis using a spatial location model based on multicriteria decision-making and geographic information systems (GIS) to identify the cultivated pasturelands most suitable for conversion to sugarcane production in Brazil. “What if” scenarios were built to determine how changes in the subjectively derived weights of the priority criteria would modify the spatial distribution of the suitability classes relative to the MCDA model and demonstrate the robustness of the crop suitability assessment. The most suitable pastureland areas for conversion to sugarcane production were predominantly located in Minas Gerais, São Paulo, Paraná, Goiás, Mato Grosso do Sul, Mato Grosso and Pará. These zones have large contiguous areas of pasture with moderate and high agricultural potentials for sugarcane production. The total estimated area of cultivated pasturelands with moderate or high suitability for sugarcane production was 50 million hectares, which is much larger than the area currently used for sugarcane production in Brazil.     

浅析2012年气象条件对达茂旗天然草场牧草生长的影响

文章分析了2012年气象条件对达茂旗天然草场牧草生长发育的影响。在主要气象条件的作用下．牧草平均高度为26cm,覆盖度65％,地上生物量1768kg／hm^2（鲜莺）,8月份然草场牧草平均高度达40cm,覆盖度75％．地上生物量3000kg／hm^2（鲜重）。     

Herbaceous layer development during spring does not deplete soil nitrogen in the Portuguese montado

Nitrogen (N) content in the soil and in the herbaceous biomass were monitored during spring of 2004-2006 to determine how the herbaceous layer development influences soil N availability in the montado ecosystem of southern Portugal. Highest (246.6 ± 52.7 g m⁻²) and lowest (123.2 ± 89.5 g m⁻²) peak biomass occurred in 2006 and 2005 respectively. Total soil N within the top 20 cm soil profile ranged between 0.2 ± 0.1% in February and 0.41 ± 0.2% in May, while available soil N was lowest (5 ± 2 μg g⁻¹soil) in February but increased three-to-five fold in March and was >17.5 μg g⁻¹soil at senescence in May. Significant (p < 0.001) increase in total N in the aboveground pool occurred between February and May. There was however, no decay in soil N content. Instead, the herbaceous vegetation enhanced soil N input and N retention in the ecosystem. Most of the herbaceous plants were annuals with large reserves of organic N at senescence, which returned to the soil as detritus. The herbaceous vegetation is a critical component of the montado that contributes to N recharge and cycling within the ecosystem.     

Mountain pastures, environmental degradation, and landscape remediation: The example of a Mediterranean policy initiative

Since the 1950s the Spanish Mediterranean mountains have undergone a process of population decline, abandonment of land by farmers, and a reduction in livestock pressure. These changes have involved pasture loss as a result of the spread of scrub and an increase in the incidence of fires. To avoid these negative outcomes the regional administration of La Rioja (Spain) has implemented scrub clearance programs. Between 1986 and 2005 a total of 23,668 ha were cleared, particularly on abandoned fields where the processes of vegetation succession had led to the dominance of Genista scorpius and Cistus laurifolius. Pasture regeneration as a result of scrub clearing of areas dominated by G. scorpius has resulted in a productivity rise from 6666 to 12,983 Mj/ha/year, whereas productivity of areas dominated by C. laurifolius has risen from 2435 to 9741 Mj/ha/year. The clearing of scrub needs to be recognized as a significant factor contributing to the control of fire. Scrub clearing has had positive results in La Rioja, leading to a reduced incidence of fires in recent years. Between 1996 and 2005 only 155 ha/year was burnt, compared with 1541 ha/year over the period from 1976 to 1985. Scrub clearing appears to be an appropriate means of management in marginal mountainous areas without the need for large investments of time and money.     

Ecological constraints on and consequences of land use heterogeneity: A case study of the Mongolian Gobi

Mongolian herders are transhumant and therefore follow a specific land use pattern. To understand their movements through a case study, we mapped and superimposed their seasonal camps on a vegetation map and a digital elevation model. We also questioned them about the reasons justifying the locations of their camps, and how they use the surrounding land. It appears that vegetation quality may play a role only in summer, whereas topography is a key driver during 3 seasons. In winter, herders seek shelter against cold winds in rugged places exposed to the south, while in spring and summer, they seek flat places. In spring, to have a clear view of their newborns and in summer, to allow wind to reduce the insect discomfort. Moreover, most of the livestock species stay within a certain distance of the camps depending on the season, but which never exceeds 5.1 km. This leads to a land use pattern where livestock is restrained to specific areas according to the season. Interestingly, during the growing season, when plants are most sensitive to defoliation, most livestock is concentrated on 30.92% of the site surface. Such information is important for range scientists working on grazing impacts at large scales.     

气候变化对青海天然牧草影响研究

根据青海省4个牧业气象代表站点1988-2005年天然牧草数据和同期气候资料,分析了青海天然牧草生长发育与气象条件的关系,探讨了气候变化对青海省牧草发育期、高度及产量形成的影响。研究表明:青南东部地区影响牧草返青出现的主要因素是热量条件,而青南西部和环湖地区牧草返青期的早晚主要受制于水分条件;两地区牧草黄枯期出现的迟早与日平均气温稳定通过5℃的终日相接近;在干旱、半干旱地区,天然牧草产量形成的主要因素取决于水分条件,年降水越多,牧草产量越高;青南东部的半湿润地区,温度对产量的影响大于降水对产量的影响。在全球气候变暖的背景下,青海省半湿润牧业区,随气温升高,牧草产量有所增加,草场载畜量有所上升;但在干旱、半干旱牧业区,气候变暖加剧草地水分的散失,牧草的生长发育受阻,产草量下降,同时,优良牧草在草场中的比例下降,杂类草的数量和比例上升,草场朝不良方向演替,呈现退化趋势。     

Effects of land-use changes on structural characteristics of tropical high-altitude Andean headwater streams

Streams are usually susceptible to land-use change, mainly in the tropics due to high dynamic climatic conditions. Native forests have been converted for agricultural purposes with significantly impacts in streams. Nowadays, forests plantations are taking place of some degraded land and its influence in headwater streams are not well understood in tropical high-altitude streams. Thus, this study aims to assess effects of land-use changes from pasture to Eucalyptus plantations in Colombian Andean catchments on stream water conditions and structural characteristics of stream channels. The study was conducted in three catchments, one catchment covered by pasture, one catchment that was converted from pasture to Eucalyptus plantations in 1995 and one pristine catchment with native forest cover. Physical, chemical and biological conditions of stream water were assessed by measurements of water temperature, concentration of dissolved oxygen and chlorophyll-a content of epiphytic communities. The structural characteristics of stream channels were evaluated using a visual-based habitat assessment protocol from the United States Environmental Protection Agency. Principal Component Analysis (PCA) showed native forest and Eucalyptus plantations catchments associated with stream conservation characteristics and pasture catchment with overall degraded conditions. However, the Permutational multivariate analysis of variance (PERMANOVA) showed significant differences between all streams indicating that, despite the overall positive conservation aspects of native and Eucalyptus catchments, their still different from each other. Pasture catchment showed the highest values for temperature and chlorophyll-a, and the lowest values for dissolved oxygen and final score for structural characteristics. Therefore, our results demonstrated that the land-use change from pasture to Eucalyptus plantation improved the stream water conditions and the structural characteristics of the studied headwater streams. Additionally, we propose the use of the rapid bioassessment protocol coupled some stream water characteristics as a rapid and useful tool for detecting effects of land-use changes on high-altitude Andean streams.     

Retrieving soil moisture in rainfed and irrigated fields using Sentinel-2 observations and a modified OPTRAM approach

Surface soil water content plays an important role in driving the exchange of latent and sensible heat between the atmosphere and land surface through transpiration and evaporation processes, regulating key physiological processes affecting plants growth. Given the high impact of water scarcity on yields, and of irrigated agriculture on the overall withdrawal rate of freshwater, it is important to define models that help to improve water resources management for agricultural purposes, and to optimize rainfed crop yield. Recent advances in satellite-based remote sensing have led to valuable solutions to estimate soil water content based on microwave or optical/thermal-infrared data. This study aims at improving soil water content estimation at high spatial and temporal resolution, by means of the Optical Trapezoid Model (OPTRAM) driven by Copernicus Sentinel-2 data. Two different model variations were considered, based on linear and nonlinear parameters constraints, and validated against in situ soil water content measurements made with time domain reflectometry (TDR) on irrigated maize in central Italy and on rainfed maize and pasture in northern Italy. For the first site the non-linear model shows a better correlation between measured and estimated soil water content values (r = 0.80) compared to the linear model (r = 0.73). In both cases the modeled soil moisture tends to overestimate the measured values at medium to high water content level, while both models underestimate soil moisture at low water content level. Estimated versus measured normalized surface soil water for rainfed pasture plots from nonlinear OPTRAM parametrized based on irrigated maize parameterization (SIM1), and site-specific parametrization for rainfed pasture (SIM2), indicate that both models (SIM1 and SIM2) are comparable for rotational grazing pasture (RMSEsim1 = 0.0581 vs. RMSEsim2 = 0.0485 cm3 cm-3) and the continuous grazing pasture (RMSEsim1 = 0.0485 vs. RMSEsim2 = 0.0602 cm3 cm-3), while for the rainfed maize plots SIM1 shows lower RMSE (average for all plots RMSE = 0.0542 cm3 cm-3) compared to the site-specific calibration model (SIM2 – average for all plots RMSE = 0.0645 cm3 cm-3). Finally, OPTRAM estimations are close to in situ measurement values while Surface Soil Moisture at 1 km (SSM1 km) tends to underestimate the measurements during maize crop growing season. Soil moisture retrieval from high-resolution Sentinel-2 optical images allows water stress conditions to be effectively mapped, supporting decision making in irrigation scheduling and other crop management.     

Discrimination of species composition types of a grazed pasture landscape using Sentinel-1 and Sentinel-2 data

Species composition is one of the important measurable indices of alpha diversity and hence aligns with the measurable Essential Biodiversity Variables meant to fulfil the Aichi Biodiversity Targets by 2020. Graziers also seek for pasture fields with varied species composition for their livestock, but visual determination of the species composition is not practicable for graziers with large fields. Consequently, this study demonstrated the capability of Sentinel-1 Synthetic Aperture Radar (S1) and Sentinel-2 Multispectral Instrument (S2) to discriminate pasture fields with single-species composition, two-species composition and multi-species composition for a pastoral landscape in Australia. The study used K-Nearest Neighbours (KNN), Random Forest (RF) and Support Vector Machine (SVM) classifiers to evaluate the strengths of S1-alone and S2-alone features and the combination of these S1 and S2 features to discriminate the composition types. For the S1 experiment, KNN which was the reference classifier achieved an overall accuracy of 0.85 while RF and SVM produced 0.74 and 0.89, respectively. The S2 experiment produced accuracies higher than the S1 in that the overall performance of the KNN classifier was 0.87 while RF and SVM were 0.93 and 0.89, respectively. The combination of the S1 and S2 features elicited the highest accuracy estimates of the classifiers in that the KNN classifier recorded 0.89 while RF and SVM produced 0.96 and 0.93, respectively. In conclusion, the inclusion of S1 features improve the classifiers created with S2 features only.