Organic matter source and degradation as revealed by molecular biomarkers in agricultural soils of Yuanyang terrace

The Biological Origins of Soil Organic Matter in Different Land-Uses in the Highlands of Ethiopia

In the Ethiopian highlands, clearance of Afromontane dry forest and conversion to crop and grazing land lead to land degradation and loss of soil organic matter (SOM). Eucalyptus is often grown on degraded soils, and this results in the partial recovery of soil carbon stocks. The aim of this work was to assess the biological sources of SOM in this land-use sequence. In top-soils (0–10 cm) of four land-use systems, namely remnant natural forest, eucalyptus plantation, cropland, and grazing land, in the Ethiopian highlands, the origin of SOM was investigated. For this, a sequential extraction method was used, involving a solvent extraction, base hydrolysis, and a subsequent CuO oxidation. In these extracts, biomarkers (molecular proxies) were identified to characterize the SOM of the soil of the four land-uses. Putative lipid monomers of leaf, root, and microbial degradation products suggest that root inputs and microbial inputs dominate in SOM of all the land-uses, except grazing land. The ratios of syringyls, vanillyls, and cinnamyls showed that non-woody angiosperm plants were the predominant source for lignin in eucalyptus, cropland, and grazing land soil. In the soils of the natural forest, lignin originates from both woody angiosperms and woody gymnosperms. Our study shows the importance of root and microbial inputs in the formation of SOM, but also that, in the natural forest, legacies of previous forest cover are present.

Wild edible plants collected by Hani from terraced rice paddy agroecosystem in Honghe Prefecture, Yunnan, China

BACKGROUND

The Hani people in the Honghe Prefecture of Southeastern Yunnan, China, have practiced terraced rice paddy farming for more than 1300 years. These rice fields, combined with the surrounding forests and water systems, form a special agroecosystem that has attracted both tourists and scientists. For centuries, the local people have traditionally collected wild edible plants (WEP) from the agroecosystem, but this unique traditional practice in this area has never been reported.

METHODS

Ethnobotanical fieldwork was conducted in four counties (Yuanyang, Honghe, Jinping, and Lüchun) between 2014 and 2019. Local self-identified Hani people (186) were interviewed, and information concerning local WEP species was obtained, documented, and analyzed. Plant samples and voucher specimens were collected for taxonomic identification.

RESULTS

A total of 224 WEP species, belonging to 90 families and 170 genera, were recorded as used by the Hani people in Honghe. The most common WEP parts used include fruits, stems, and leaves, and the most common preparation methods include eating as a potherb (wild vegetable) and eating fresh. Some WEPs, like Phyllanthus emblica and Dioscorea subcalva, have unique preparation methods. The use-value (UV) and frequency of utilization index (FUI) of WEP species were analyzed. The 20 WEP species with the highest UV were noted as particularly important to the Hani people's daily life in Honghe.

CONCLUSION

A large majority of these WEP species possess tremendous economic potential for future development. However, the diversity of WEP species, the associated traditional knowledge, and the broader agroecosystem are facing challenges such as biodiversity loss and pollution from chemical pesticides and fertilizers. This study may help local people to recognize the value of local WEP species and associated traditional knowledge, as well as provide ethnobotanical information for the future development of this tourism region.

Wild edible plants collected by Hani from terraced rice paddy agroecosystem in Honghe Prefecture, Yunnan, China

BACKGROUND

The Hani people in the Honghe Prefecture of Southeastern Yunnan, China, have practiced terraced rice paddy farming for more than 1300 years. These rice fields, combined with the surrounding forests and water systems, form a special agroecosystem that has attracted both tourists and scientists. For centuries, the local people have traditionally collected wild edible plants (WEP) from the agroecosystem, but this unique traditional practice in this area has never been reported.

METHODS

Ethnobotanical fieldwork was conducted in four counties (Yuanyang, Honghe, Jinping, and Lüchun) between 2014 and 2019. Local self-identified Hani people (186) were interviewed, and information concerning local WEP species was obtained, documented, and analyzed. Plant samples and voucher specimens were collected for taxonomic identification.

RESULTS

A total of 224 WEP species, belonging to 90 families and 170 genera, were recorded as used by the Hani people in Honghe. The most common WEP parts used include fruits, stems, and leaves, and the most common preparation methods include eating as a potherb (wild vegetable) and eating fresh. Some WEPs, like Phyllanthus emblica and Dioscorea subcalva, have unique preparation methods. The use-value (UV) and frequency of utilization index (FUI) of WEP species were analyzed. The 20 WEP species with the highest UV were noted as particularly important to the Hani people's daily life in Honghe.

CONCLUSION

A large majority of these WEP species possess tremendous economic potential for future development. However, the diversity of WEP species, the associated traditional knowledge, and the broader agroecosystem are facing challenges such as biodiversity loss and pollution from chemical pesticides and fertilizers. This study may help local people to recognize the value of local WEP species and associated traditional knowledge, as well as provide ethnobotanical information for the future development of this tourism region.

Distribution of organic carbon and lignin in soils in a subtropical small mountainous river basin

As a unique biomarker of terrigenous organic matter (OM), lignin has provided valuable information for tracing the sources of OM in land to ocean transfer. Oceanian small mountainous rivers (SMRs) are characterized by extremely high erosional rate and quick change in microclimate within watershed, which may potentially affect the distribution of soil OC and lignin concentrations and compositions. Bulk OC% and lignin were determined on surface soils and soil profiles from a Taiwanese SMR (Jhuoshuei River) and nearby region along a large altitudinal gradient (3-3176 m) to investigate the influence of microclimate on soil OC and lignin. Both surface soils OC% and lignin increased in higher altitude, suggesting higher preservation of OM in the cold region. Variations in lignin vegetation indices (S/V and C/V) in surface soils generally reflect the vegetation change in this river basin, and were more affected by precipitation seasonality than mean annual precipitation. Lignin concentration decreased with depth, along with a decrease in S/V and C/V and an increase in degradation indices ((Ad/Al)v and DHBA/V), reflecting a decreased input and/or biodegradation of lignin in subsoils. Our survey on soil lignin in Taiwan SMR provided the basis for utilizing lignin to trace the source of OC in land to ocean transfer as well as paleo-climate and paleo-vegetation reconstruction study in Taiwan SMRs.