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The only location for the protection of Arowana golden-red in its natural habitat is in east-central Sumatra. Currently, the area is being invaded by oil palm plantations. This research identified the present conditions in that conservation area, specifically focusing on land-use situation and aquatic organism distribution and diversity. We designated four sampling sites according to the stratification of river flows that pass through the Arowana golden-red conservation area and present land use. The research showed that oil palm plantation was the largest land use in the Arowana golden-red conservation area covering 61.2% (2,310.84 ha). The swamp forest which is the habitat of Arowana golden-red only remained at 6.99% (263.98 ha). In the study area, aquatic organisms were identified as 47 species with a total of 424 individuals: 7 genera of Benthos, 11 species of Planktonic algae, and 29 species of Fish. The diversity index was in the range of 0.46–2.45. The diversity of aquatic organisms was found to be comparable to or higher than other areas in Malaysia and Indonesia such as Aceh province and Kalimantan. However, only 31 individuals of Arowana golden-red were found in the swamp forest in Middle Mahato. This site should be a priority area to save the Arowana golden-red. [ABSTRACT FROM AUTHOR]

In arid Africa, it is unclear how the transition from grassland to cropland affects CO2 fluxes and whether these effects are climate-dependent. From November 2019 to March 2020 (dry season), we studied autotrophic (Ra) and heterotrophic (Rh) soil respiration. At highlands, grazing land (1.18 ± 0.13 µmol m−2 s−1) and teff croplands (1.36 ± 0.14 µmol m−2 s−1) had the lowest Rh, while acacia decurrens plantations (1.94 ± 0.19 µmol m−2 s−1) were the largest. When compared to teff (2.08 ± 0.20 µmol m−2 s−1) and khat (1.73 ± 0.24 µmol m−2 s−1), grazing land in the midland had a lower Rh (1.18 ± 0.13 µmol m−2 s−1). Ra on teff (1.51 ± 0.27 µmol m−2 s−1) was substantially (P < 0.05) greater than on grazing land (1.08 ± 0.32 µmol m−2 s−1) in the highlands. Grazing lands (1.54 ± 0.21 µmol m−2 s−1) have a considerably (P < 0.05) greater Ra than farmlands (teff, 0.20 ± 0.07 µmol m−2 s−1; groundnut, 0.09 ± 0.03 µmol m−2 s−1) in lowlands. Growing teff in the highlands and midlands will result in higher CO2 fluxes into the atmosphere. However, in-depth research is needed to implement effective land management that reduces CO2 emissions. [ABSTRACT FROM AUTHOR]

Silicon is a beneficial element for rice plants and is one of the major factors affecting the sustainability of rice production. We investigated silica (Si) availability and dynamics in soils of sawah, other land uses, and also in river and canal water in two watersheds in Citarum and Kaligarang, Java Island, Indonesia. The term sawah refers to a leveled and bounded rice field with an inlet and an outlet for irrigation and drainage, respectively. In the present study, we examined Si content in soils, plants and river water in relation to factors influencing the Si content, such as parent material and land use. The available Si content in sawah was found to be deficient at two sites and low at 10 sites out of 16 sites investigated in the Citarum watershed. In the Kaligarang watershed, no sawah site was classified as deficient and nine out of the 15 sawah sites were determined to be low for rice plant growth. A survey of Si content in rice flag leaves in some selected rice fields showed that seven out of 12 samples had contents less than 125 g SiO2 kg−1; these rice samples with low Si contents were those in sawah classified as low in Si contents. In the Citarum watershed, sawah soils developed from the accumulation of lake and clay sediment contained relatively little available Si, while sawah soils in the Kaligarang watershed that were mainly developed from tuff and volcanic ash contained relatively more available Si. In the Citarum watershed, the type of land use influenced Si availability in the soils via a large amount of litter accumulation of pine trees in the case of pine plantations, and acidification in the soils in the case of tea plantations and maize fields. In general, the Si content in river and canal water was higher in the Kaligarang watershed than in the Citarum watershed, and this appears to be affected by the type of parent material. In addition to the type of parent material, Si depletion occurring in dams might also influence Si content in the lower stream of river or canal water in the Citarum watershed. [ABSTRACT FROM AUTHOR]

The present study investigated macro- and micronutrient status in the soils under the native forest (NF), cropland (CL) and rangeland over 27 years in Colonia Okinawa, Santa Cruz, Bolivia, in order to assess the effect of land use on soil fertility in the region. The C, N and P pools in the soil of CL were less by 60, 57 and 27% as compared to NF, respectively. The rangeland with Panicum maximum (RG) showed almost similar values of C, N and P pools to CL, while the values in the rangeland with Paspalum notatum (RB) were relatively closer to NF. Mehlich-3 extractable P, Ca and Mg considerably declined in CL, RG and RB, but an inverse trend was observed in Mehlich-3 extractable K probably due to the stimulation of weathering of illite in the soil. Mehlich-3 extractable Mn, Fe and Cu were tended to increase in RG and RB, which suggested possible accumulation of these metals because of the manure deposited by grazing cattle on the rangelands. Besides C, N and P pools, the values of Mehlich-3 extractable K, Mn, Fe and Zn were less in RG than RB because of greater exploitation of these nutrients in RG than RB. There was a significant correlation between C, N, P, Ca, Mg and Zn suggesting that the dynamics of these components could be associated with the organic matter in the soil. The findings of this study clarified the soil chemical degradation in the cropland and rangeland. However, the magnitude of the land chemical deterioration under the rangeland was highly variable depending on the grass species. [ABSTRACT FROM AUTHOR]

• LULC changes, drivers and implications were examined (1982-2016/2017) in contrasting agro-ecologies. • Cultivated land has progressively increased in the first three decades across all agro-ecologies. • After 2012, A. decurrence has increased by 400% at the expense of cultivated land in highland agroecology (Guder). • Population growth associated with changing farming practices were the major drivers for LULC changes. • The expansion of cultivated land had aggravated the soil erosion and surface runoff in the watersheds. This study examined the trends, driving factors, and implications of land use/land cover (LULC) dynamics over the past 35 years (1982–2017) in three watersheds of the drought-prone areas that represent different agro-ecologies of Upper Blue Nile basin, Ethiopia: Guder (highland), Aba Gerima (midland), and Debatie (lowland). The changes in LULC were analyzed by integrating field observations, remote-sensing data (aerial photographs [1: 50,000 scale] and very high resolution [0.5–3.2 m] satellite images), and geographic information systems. The drivers of LULC were explored using key informant interviews and relevant literature reviews. The implications of LULC change on soil erosion and surface runoff responses were also evaluated. A minimum of four and maximum of six LULC classes were identified in each watershed over the study period. The study revealed that forest land was the dominant LULC class accounting for 40.9% and 32.0% in Guder and Aba Gerima, respectively in 1982. While in the same period, bush land (36.6%) was the dominant LULC class in Debatie watershed. From 1982 to 2016/2017, forest land, bush land, and grazing land respectively decreased by about 70%, 50%, and 27% in Guder; 65%, 49%, and 63% in Aba Gerima; and 63%, 59%, and 38% in Debatie. During the same period, cultivated land increased by approximately 40%, 129%, and 704% in Guder, Aba Gerima and Debatie, respectively. In contrast, between 2012 and 2017, plantation cover increased by about 400% in the Guder, mainly at the expense of cultivated land, which decreased by 40% for the same period. Population growth and associated changes in the farming practices were the major driving forces for the observed LULC changes in the study watersheds. The traditionally deleterious impacts of human activities on the environment have been recently reversed at an unprecedented rate, particularly at Guder and to a lesser extent at Aba Gerima, following the shift from the traditional annual cropping to more economically attractive tree-based farming practices such as Acacia decurrens plantation in Guder and khat (Catha edulis) cultivation in Aba Gerima. The continued expansion of cultivated land combined with population growth positively linked to the increase of gully erosion and surface runoff potential in the study watersheds particularly, in Aba Gerima and Debatie watersheds. The Upper Blue Nile basin is currently experiencing both positive and negative socio-economic and environmental consequences of LULC dynamics. Hence, the present study can help form a basis for the appropriate development of land management policies and strategies in this and other basins experiencing similar problems. [ABSTRACT FROM AUTHOR]

• Soil properties significantly varied across agro-ecologcal zones & land uses types. • Croplands exhibited low values of most soil quality property parameters. • Sustainable land management practices improved sensitive soil properties. • Exlcosure substantially improved soil organic carbon and total nitrogen contents. The knowledge of how soil properties vary over space and time is essential to better understand the potential of soils and their sensitivity to management interventions under different local conditions. The objective of this study was to analyze the variation in key soil properties as influenced by different land use types (cropland, grazing land, and bushland) and sustainable land management (SLM) practices (soil bund reinforced with grass, and fanya juu for croplands, and exclosures with and without trenches for grazing and bushlands) in the three contrasting agro-ecological zones of the drought-prone Upper Blue Nile basin, Ethiopia. Nine soil properties—texture, bulk density (BD), pH, electrical conductivity (EC), cation exchange capacity (CEC), total nitrogen (TN), soil organic carbon (SOC), available phosphorus (P av), and available potassium (K av)—were measured for topsoil (0–20 cm) samples collected from experimental plots established for monitoring runoff and soil loss rates. The results showed that seven of the nine studied soil properties significantly differed among the three land use types in the three agro-ecological zones (P < 0.05 to P < 0.001); pH, CEC, SOC, and TN values were generally lower in croplands than in others. These results imply that soil quality under crop production has been greatly deteriorated by unsustainable cropping systems practiced over centuries. Three years after the implementation of SLM practices, however, most soil parameters become within optimal ranges for supporting plant production. More particularly, sensitive soil properties (BD, SOC, TN, P av , and K av) showed remarkable improvement in plots where soil bunds reinforced with grass and exclosures were implemented. This improvement was primarily associated with the development of well-established vegetation cover owing to the favorable natural conditions maintained by fencing of plots and minimum tillage. These results therefore indicate that soil degradation can best be controlled through enhancing vegetation growth and reducing soil disturbance by tillage operations. We conclude that integrating land uses with suitable SLM practices is the most effective way to maintain and restore soil quality and sustain ecosystem functioning. [ABSTRACT FROM AUTHOR]