Land-Use Change Depletes Quantity and Quality of Soil Organic Matter Fractions in Ethiopian Highlands

The depletion of soil organic matter (SOM) reserve after deforestation and subsequent management practices are well documented, but the impacts of land-use change on the persistence and vulnerability of storage C and N remain uncertain. We investigated soil organic C (SOC) and N stocks in a landscape of chrono-sequence natural forest, grazing/crop lands and plantation forest in the highlands of North-West Ethiopia. We hypothesized that in addition to depleting total C and N pools, multiple conversions of natural forest significantly change the relative proportion of labile and recalcitrant C and N fractions in soils, and thus affect SOM quality. To examine this hypothesis, we estimated depletion of SOC and N stocks and labile (1 & 2) and recalcitrant (fraction 3) C and N pools in soil organic matter following the acid hydrolysis technique. Our studies showed the highest loss of C stock was in grazing land (58%) followed by cropland (50%) and eucalyptus plantation (47%), while on average ca. 57% N stock was depleted. Eucalyptus plantation exhibited potential for soil C recovery, although not for N, after 30 years. The fractionation of SOM revealed that depletions of labile 1 C stocks were similar in grazing and crop lands (36%), and loss of recalcitrant C was highest in grazing soil (56%). However, increases in relative concentrations of labile fraction 1 in grazing land and recalcitrant C and N in cropland suggest the quality of these pools might be influenced by management activities. Also, the C:N ratio of C fractions and recalcitrant indices (RIC and RIN) clearly demonstrated that land conversion from natural forest to managed systems changes the inherent quality of the fractions, which was obscured in whole soil analysis. These findings underscore the importance of considering the quality of SOM when evaluating disturbance impacts on SOC and N stocks.

Potential of peat carbon storage in natural forests Tripa Peat Swamp at Aceh Barat Daya District

Carbon storage is the total weight of carbon stored in the ecosystem at a certain time, especially in natural forests in the Tripa peat swamp area of Aceh Barat Daya. Peatlands are wetland ecosystems that are formed by the accumulation of organic matter on the forest floor from weathering of the vegetation on it over a long period of time. The research objectives were 1) to calculate peat soil carbon storage and 2) to measure the depth of peat soil in natural forest in the Tripa peat swamp area, Aceh Barat Daya Regency. The research activity was carried out from February to March 2021, in a natural forest in the Tripa Aceh Barat peat swamp area, divided into three stations and at each station, three sampling plots were made. Data collection using purposive sampling technique, Analysis of carbon stock was analyzed using the formula for calculating carbon stock by entering data on the percentage of soil organic carbon in the laboratory, and data on peat depth in a descriptive analysis. The results showed that the amount of peat soil carbon storage, especially in natural forest in the Tripa Aceh Barat Daya peat swamp area, was 2.556 tons/ha and the peat depth range was fibric with a depth of 0-95 cm, hemic 96-292 cm, and substance 293-310.

Interação dos atributos químicos do solo em área com floresta natural e com plantio de laranja (Citrus sinensis L Osb.)

Na região amazônica é comum a conversão de ambiente natural para o de cultivo, com isso o solo permanece em constantes modificações. As atividades agrícolas podem incrementar a heterogeneidade do solo provocando alterações nos atributos químicos do solo, decorrente principalmente das atividades de manejo e cultivo. Essas mudanças são mensuráveis e contribuem para caracterizar, avaliar e acompanhar as alterações ocorrida utilizando ferramentas estatísticas. Assim o estudo da variabilidade espacial dos atributos químicos dos solos é particularmente importante especialmente em áreas onde o solo está submetido a diferentes manejos, visando reduzir os efeitos da variabilidade na produção das culturas em função de determinadas práticas de manejo. Dessa forma, este trabalho tem por objetivo avaliar a variabilidade espacial dos atributos químicos em área de floresta natural e com cultivo de laranja em Colorado do Oeste, Rondônia. Foram selecionadas duas áreas de estudo, a primeira sendo a área de floresta nativa e a segunda sob cultivo de laranja em de Colorado do Oeste, Rondônia. Em cada área foi delimitada uma malha com 1.260 m² (42 x 30 m), com 48 pontos e espaçamento regular entre pontos de 6 m. Nos pontos de cruzamento da malha foram coletadas amostras em três profundidades (0,00-0,05; 0,05-0,10 e 0,10-0,20 m), correspondente ao horizonte diagnóstico do solo, perfazendo uma somatória de 144 amostras por área, logo, um total de 288. Serão determinados dos atributos químicos de pH em água, acidez potencial, alumínio trocável, fósforo e potássio disponível, e carbono orgânico. Com a obtenção dos dados, estes foram avaliados por meio de estatística descrita com teste de médias e a realização da análise multivariada. Houve diferença entre as duas áreas, a substituição da vegetação nativa por sistema de cultivo, ocasionou alterações nos atributos químicos do solo. O uso das técnicas multivariadas mostrou-se eficiente na distinção dos ambientes estudados. Interaction of the chemical attributes of the soil in an area with natural forest and with planting of orange (Citrus sinensis L. Osb.) A B S T R A C TIn the Amazon region it is common to convert from a natural environment to that of cultivation, with this the soil remains in constant modifications. Agricultural activities can increase the heterogeneity of the soil causing changes in the chemical attributes of the soil, mainly due to management and cultivation activities. These changes are measurable and contribute to characterize, evaluate and monitor the changes that have occurred using statistical tools. Thus, the study of the spatial variability of the chemical attributes of soils is particularly important, especially in areas where the soil is subjected to different managements, in order to reduce the effects of variability in the production of crops due to certain management practices. Thus, this work aims to evaluate the spatial variability of chemical attributes in an area of natural forest and with orange cultivation in Colorado do Oeste, Rondônia. Two study areas were selected, the first being the native forest area and the second under orange cultivation in Colorado do Oeste, Rondônia. In each area, a mesh of 1,260 m² (42 x 30 m) was delimited, with 48 points and regular spacing between points of 6 m. At the crossing points of the grid, samples were collected at three depths (0.00-0.05; 0.05-0.10 and 0.10-0.20 m), corresponding to the soil diagnostic horizon, making a sum of 144 samples per area, therefore, a total of 288. The chemical attributes of pH in water, potential acidity, exchangeable aluminum, available phosphorus and potassium, and organic carbon will be determined. Once the data were obtained, they were evaluated using statistics described with the means test and the multivariate analysis. There was a difference between the two areas, the replacement of native vegetation by a cultivation system, caused changes in the chemical attributes of the soil. The use of multivariate techniques proved to be efficient in distinguishing the studied environments.Keywords: Amazon soils, Use and management, Soil occupation.

Deciphering Rhizosphere Microbiome Assembly of Castanea henryi in Plantation and Natural Forest

Based on the importance and sensitivity of microbial communities to changes in the forest ecosystem, soil microorganisms can be used to indicate the health of the forest system. The metagenome sequencing was used to analyze the changes of microbial communities between natural and plantation Castanea henryi forests for understanding the effect of forest types on soil microbial communities. Our result showed the soil microbial diversity and richness were higher in the natural forests than in the plantation. Proteobacteria, Actinobacteria, and Acidobacteria are the dominant categories in the C. henryi rhizosphere, and Proteobacteria and Actinobacteria were significantly enriched in the natural forest while Acidobacteria was significantly enriched in the plantation. Meanwhile, the functional gene diversity and the abundance of functions in the natural forest were higher than that of the plantation. Furthermore, we found that the microbial network in the natural forests had more complex than in the plantation. We also emphasized the low-abundance taxa may play an important role in the network structure. These results clearly showed that microbial communities, in response to different forest types, provide valuable information to manipulate microbiomes to improve soil conditions of plantation.

ESTIMASI POTENSI KARBON SEDIMEN MANGROVE PADA HUTAN ALAM DAN HUTAN REHABILITASI DI TAMAN HUTAN RAYA NGURAH RAI BALI

Sediments play an important role in coastal ecosystems. Apart from being a growing medium, sediment is also a place for accumulation and storage of various components including carbon. Ngurah Rai Forest Park is the largest mangrove in Bali with a large potential for sediment carbon stocks. To determine the carbon storage of mangrove sediments in natural forest and rehabilitation forest and the relationship between diameter size and vegetation type to sediment carbon in two forest types, a study was conducted using purposive sampling method based on canopy density level with three repetitions with a plot size of 10 mx. 10 meters. Sampling was divided into three depths, namely 0-30 cm, 31-60 cm and 61-100 cm. The total carbon content of mangrove sediments in natural forest is 363,491.17 Mg C or equivalent to 363,491.17 tons C and rehabilitation forest is 160,401.33 Mg C or equivalent to 160,401.33 tons C. The total sediment carbon content in Ngurah Rai Forest Park is 523,892.50 Mg C or equivalent to 523,892.50 tons C. Tree diameter had no significant effect on sediment carbon content, while vegetation type significantly affected sediment carbon content. Sonneratia alba had a significant negative effect on natural forests, while Rhizophora stylosa had a significant positive effect on rehabilitation forests. The results of the study suggest that it is necessary to maintain the preservation of mangroves and carry out rehabilitation in damaged areas. To increase the carbon content of sediments in mangrove forests, consider selecting the type of vegetation Rhizophora stylosa for the implementation of rehabilitation activities, because the type of Rhizophora stylosa makes a positive contribution to increasing the carbon content of sediments, with a note that the rehabilitation location is suitable for Rhizoporaceae species. Keywords: Mangrove; Nature Forest; Rehabilitation; Sediment.

ESTIMASI KANDUNGAN KARBON ATAS PERMUKAAN TANAH PADA HUTAN ALAM DAN HUTAN REHABILITASI MANGROVE TAMAN HUTAN RAYA NGURAH RAI BALI

Mangroves are ecosystems that play an important role in absorbing and storing carbon from the air, one of which is in the form of mangrove vegetation biomass. As the largest mangrove area in Bali which consists of natural and rehabilitation vegetation, Taman Hutan Raya Ngurah Rai has a large potential for high carbon content. To determine the carbon potential of mangroves in natural and rehabilitation forests, a research was conducted using the purposive sampling method based on the canopy density level which was divided into 5 categories, namely very rare, rare, moderate, dense, very dense. Based on the results of measurements and calculations, the total carbon content of Ngurah Rai Grand Forest Park is 86.521,74 tons C, consisting of natural forest content 66.857,53 tons C and rehabilitation forest 19.664,21 tons C. Above ground carbon per hectare in natural forest was not significantly different from the above ground carbon per hectare in rehabilitation forest, these results indicate that the carbon content per hectare of rehabilitation forest over 20 years old is almost close to the carbon content per hectare in natural forest. The diameter of trees and vegetation types did not significantly affect the carbon content of mangroves, these results indicate that the increase in carbon stocks in each type of vegetation in natural and rehabilitation forests is in line with diameter growth. Keywords: Biomass; Density; Diameter; Canopy.