Responses of plant functional types to environmental gradients in the south-west Ethiopian highlands

2011 ◽  
Vol 27 (03) ◽  
pp. 289-304 ◽  
Author(s):  
Desalegn Wana ◽  
Carl Beierkuhnlein
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Relative Abundance ◽  
Environmental Variables ◽  
Environmental Gradients ◽  
Plant Functional Types ◽  
The South ◽  
Ethiopian Highlands ◽  
South West ◽  
Functional Types

Abstract:Plant functional types across environmental gradients can be considered as a powerful proxy that reveals vegetation–environment relationships. The objectives of this study were to investigate the response in the relative abundance of plant functional types along altitudinal gradients and to examine the relationship of plant functional types to environmental variables. The study was conducted in the Gughe-Amaro Mountains, in the south-west Ethiopian highlands. We established 74 plots with an area of 400 m2(20 × 20 m) each along altitudinal ranges between 1000 and 3000 m asl. Data on site environmental conditions and on the abundance of plant functional types were analysed using the constrained linear ordination technique (RDA) in order to identify the relationships between plant functional types and environmental variables. Altitude, soil organic carbon, soil sand fraction and surface stone cover were significantly related to the relative abundance of plant functional types across the gradient. Tussocks and thorns/spines were abundant in lower altitudinal ranges in response to herbivory and drought while rhizomes and rosettes were abundant at higher altitudes in response to the cold. Generally our results show that topographic attributes (altitude and slope) as well as soil organic carbon play an important role in differentiating the relative abundance of plant functional types in the investigated gradient. Thus, considering specific plant functional types would provide a better understanding of the ecological patterns of vegetation and their response to environmental gradients in tropical regions of Africa prone to drought.

Estimating the economic value of soil organic carbon for grains cropping systems in Western Australia

Soil Research ◽  
2016 ◽  
Vol 54 (4) ◽  
pp. 383 ◽  
Author(s):  
E. H. Petersen ◽  
F. C. Hoyle
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Western Australia ◽  
Production Systems ◽  
Cropping Systems ◽  
Economic Value ◽  
Practice Change ◽  
The South ◽  
Marginal Value ◽  
South West

Soil organic carbon (SOC) has the potential to benefit soil function and fertility, and in agricultural production systems, it is considered integral to sustainable farming. We analyse the value of SOC in cropping systems of the south-west of Western Australia in terms of agronomic benefits from increasing productivity (through increased plant-available water-holding capacity) and reducing fertiliser use (due to increased mineralisation of nitrogen). We also present the potential value of SOC in terms of sequestration benefit if landholders were able to participate in a carbon-sequestration program. We estimate the marginal value of SOC (the value of a soil with more SOC, by 1 t C/ha, than a standard soil) to be AU$7.1–8.7/t C.ha.year, depending on rainfall zone and crop type. Approximately 75% of this value is the estimated sequestration value, 20% is the nitrogen-replacement value, and 5% is the estimated productivity improvement value. Over 50 years, this equates $130–160/t C.ha depending on the rainfall zone. These values are sensitive to variations in fertiliser and carbon prices. Our results imply this it is unlikely that the SOC benefits will drive practice change in the south-west of Western Australia.

Biogeochemical processes and labile composition of settling particulate organic matter in the south-west Pacific Ocean

2003 ◽  
Vol 54 (3) ◽  
pp. 259 ◽  
Author(s):  
Lallan Prasad Gupta ◽  
Hodaka Kawahata
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Particulate Organic Matter ◽  
Deep Trap ◽  
Biogeochemical Processes ◽  
Shallow Trap ◽  
The South ◽  
Coral Sea ◽  
South West ◽  
Tasman Sea

Settling particles collected by sediment traps deployed for approximately 1 year in the Coral Sea and Tasman Sea were analysed to understand the biogeochemical processes controlling the cycling and flux of particulate organic matter (POM) in the south-west Pacific. Samples were analysed for 20 amino acids (AA) and two hexosamines (HA) and the data were interpreted together with already published data on opal (biogenic silica), organic carbon and total nitrogen contents. Mean fluxes of labile carbon and nitrogen at one site were significantly different (P < 0.04, t-test; n = 14–18) from those at other sites. The southernmost trap recorded the highest concentrations of AA, HA and organic carbon normalized AA. At a site in the south, POM was more degraded in the deep trap than in the shallow trap. Occasionally, higher fluxes were also recorded at the deep trap relative to the shallow trap. The C/Natomic ratio coupled with AA- and HA-based parameters clearly suggested contribution of POM through resuspension as well as lateral advection at the more southern site, whereas a strong influence of zooplankton on total mass flux was revealed at the northern site during the period August–September 1995. It is evident from the data that higher flux of particles having higher labile contents (AA and HA) is more prevalent in the Tasman Sea than in the Coral Sea.

Spatial modelling of soil organic carbon stocks with combined principal component analysis and geographically weighted regression

2018 ◽  
Vol 156 (6) ◽  
pp. 774-784 ◽  
Author(s):  
Long Guo ◽  
Mei Luo ◽  
Chengsi Zhangyang ◽  
Chen Zeng ◽  
Shanqin Wang ◽  
...  
Keyword(s):  
Principal Component Analysis ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Geographically Weighted Regression ◽  
Environmental Variables ◽  
Prediction Models ◽  
Principal Component ◽  
Weighted Regression ◽  
Auxiliary Variables ◽  
Soc Stocks

AbstractWith the development of remote sensing and geostatistical technology, complex environmental variables are increasingly easily quantified and applied in modelling soil organic carbon (SOC). However, this emphasizes data redundancy and multicollinearity problems adding to the difficulty in selecting dominant influential auxiliary variables and uncertainty in estimating SOC stocks. The current paper considers the spatial characteristics of SOC density (SOCD) to construct prediction models of SOCD on the basis of reducing the data dimensionality and complexity using the principal component analysis (PCA) method. A total of 260 topsoil samples were collected from Chahe town, China. Eight environmental variables (elevation, aspect, slope, normalized difference vegetation index, normalized difference moisture index, nearest distance to construction area and road, and land use degree comprehensive index) were pre-analysed by PCA and then extracted as the main principal component variables to construct prediction models. Two geostatistical approaches (ordinary kriging and ordinary co-kriging) and two regression approaches (ordinary least squares and geographically weighted regression (GWR)) were used to estimate SOCD. Results showed that PCA played an important role in reducing the redundancy and multicollinearity of the auxiliary variables and GWR achieved the highest prediction accuracy in these four models. GWR considered not only the spatial characteristics of SOCD but also the related valuable information of the auxiliary attributes. In summary, PCA-GWR is a promising spatial method used here to predict SOC stocks.

Predicting soil organic carbon density using auxiliary environmental variables in northern Iran

2015 ◽  
Vol 62 (3) ◽  
pp. 375-393 ◽  
Author(s):  
Samereh Falahatkar ◽  
Seyed Mohsen Hosseini ◽  
Shamsollah Ayoubi ◽  
Abdolrassoul Salmanmahiny
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Environmental Variables ◽  
Carbon Density ◽  
Northern Iran ◽  
Soil Organic Carbon Density

Fluctuations in the herring and pilchard fisheries of devon and cornwall linked to change in climate since the 16th century

1988 ◽  
Vol 68 (3) ◽  
pp. 423-445 ◽  
Author(s):  
A. J. Southward ◽  
G. T. Boalch ◽  
Linda Maddock
Keyword(s):  
Seventeenth Century ◽  
Competitive Advantage ◽  
Relative Abundance ◽  
Scientific Data ◽  
South Coast ◽  
16Th Century ◽  
Direct Effects ◽  
The South ◽  
South West ◽  
Behaviour Changes

Scientific data from the last 100 years are combined with primary and secondary historical information on the fisheries to summarize changes in the relative abundance of pilchards and herrings in the south-west in the last 400 years. The fluctuations in the two species are compared with recorded and inferred annual mean temperatures over the period. Pilchards are more abundant and extend farther to the east when the climate is warmer, as from 1590 to 1640 and from 1930 to 1960. In cooler times, as in the second half of the seventeenth century, herrings are more abundant while the pilchard fishery occurs later in the year and is restricted to west Cornwall. Lesser changes in the relative abundance of the two species and the timing of the fishery along the south coast of Devon and Cornwall in the intervening periods between these extremes accord fairly well with smaller fluctuations in climate. It is presumed that in addition to direct effects on reproduction and behaviour, changes in climate can indirectly influence the relative competitive advantage of the species through alterations in the associated ecosystem.

scholarly journals Investigating Spatial and Vertical Patterns of Wetland Soil Organic Carbon Concentrations in China’s Western Songnen Plain by Comparing Different Algorithms

2020 ◽  
Vol 12 (3) ◽  
pp. 932 ◽  
Author(s):  
Yongxing Ren ◽  
Xiaoyan Li ◽  
Dehua Mao ◽  
Zongming Wang ◽  
Mingming Jia ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Land Surface ◽  
Environmental Variables ◽  
Support Vector ◽  
Wetland Soil ◽  
Songnen Plain ◽  
Attribute Importance ◽  
Organic Carbon Concentration ◽  
Different Depths

Investigating the spatial and vertical patterns of wetland soil organic carbon concentration (SOCc) is important for understanding the regional carbon cycle and managing the wetland ecosystem. By integrating 160 wetland soil profile samples and environmental variables from climatic, topographical, and remote sensing data, we spatially predicted the SOCc of wetlands in China’s Western Songnen Plain by comparing four algorithms: random forest (RF), support vector machine (SVM) for regression, inverse distance weighted (IDW), and ordinary kriging (OK). The predicted results of the SOCc from the different algorithms were validated against independent testing samples according to the mean error, root mean squared error, and correlation coefficient. The results show that the measured SOCc values at depths of 0–30, 30–60, and 60–100 cm were 15.28, 7.57, and 5.22 g·kg−1, respectively. An assessment revealed that the RF algorithm was most accurate for predicting SOCc; its correlation coefficients at the different depths were 0.82, 0.59, and 0.51, respectively. The attribute importance from the RF indicates that environmental variables have various effects on the SOCc at different depths. The land surface temperature and land surface water index had a stronger influence on the spatial distribution of SOCc at the depths of 0–30 and 30–60 cm, whereas topographic factors, such as altitude, had a stronger influence within 60–100 cm. The predicted SOCc of each vertical depth increased gradually from south to north in the study area. This research provides an important case study for predicting SOCc, including selecting factors and algorithms, and helps with understanding the carbon cycles of regional wetlands.

scholarly journals Spatial-Temporal Changes in Soil Organic Carbon and pH in the Liaoning Province of China: A Modeling Analysis Based on Observational Data

2019 ◽  
Vol 11 (13) ◽  
pp. 3569 ◽  
Author(s):  
Li Qi ◽  
Shuai Wang ◽  
Qianlai Zhuang ◽  
Zijiao Yang ◽  
Shubin Bai ◽  
...  
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Environmental Variables ◽  
Spatial Variations ◽  
Liaoning Province ◽  
Mean Annual Precipitation ◽  
Topographic Wetness Index ◽  
Infrared Band ◽  
Wetness Index

Quantification of soil organic carbon (SOC) and pH, and their spatial variations at regional scales, is a foundation to adequately assess agriculture, pollution control, or environmental health and ecosystem functioning, so as to establish better practices for land use and land management. In this study, we used the random forest (RF) model to map the distribution of SOC and pH in the topsoil (0–20 cm) and estimate SOC and pH changes from 1982 to 2012 in Liaoning Province, Northeast China. A total of 10 covariates (elevation, slope gradient, topographic wetness index (TWI), mean annual temperature (MAT), mean annual precipitation (MAP), visible-red band 3 (B3), near-infrared band 4 (B4), short-wave infrared band 5 (B5), normalized difference vegetation index (NDVI), and land-use data) and a set of 806 (in 1982) and 973 (in 2012) soil samples were selected. Cross-validation technology was used to test the performance and uncertainty of the RF model. We found that the prediction R2 of SOC and pH was 0.69 and 0.54 for 1982, and 0.63 and 0.48 for 2012, respectively. Elevation, NDVI, and land use are the main environmental variables affecting the spatial variability of SOC in both periods. Correspondingly, the topographic wetness index and mean annual precipitation were the two most critical environmental variables affecting the spatial variation of pH. The mean SOC and pH decreased from 18.6 to 16.9 kg−1 and 6.9 to 6.6, respectively, over a 30-year period. SOC distribution generated using the RF model showed a decreasing SOC trend from east to west across the city in the two periods. In contrast, the spatial distribution of pH showed an opposite trend in both periods. This study provided important information of spatial variations in SOC and pH to agencies and communities in this region, to evaluate soil quality and make decisions on remediation and prevention of soil acidification and salinization.

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