Mapping Changes in Carbon Storage and Productivity Services Provided by Riparian Ecosystems of Semi-Arid Environments in Northwestern Mexico

Abstract

We analyze the importance of riparian ecosystems (RE) as critical areas for carbon storage and productivity in semi-arid regions of Northwest Mexico. We calculated the carbon storage by land cover and compared temporal trends of basal productivity (MODIS) and pre-monsoon productivity (Landsat) of RE, to other land cover types. We used land cover maps generated previously for the region (years 1993, 2002, and 2011), assigning values of carbon stored in aerial and root biomass, as well as organic carbon stored in the soil. To estimate productivity (proxy), time series were generated using the Normalized Difference Vegetation Index (NDVI) values of Landsat 4-5 TM and MODIS for each land cover type. We found that RE stores 93,147 tC/ha, about 1.5 times the estimated storage for oak forest (65,048 tC/ha). Productivity of RE was similar to highly productive land cover types, such as agriculture and oak forest, and higher than in the rest of the ecosystems of the region. We also found that changes from RE to agriculture and cultivated grasslands represented a decrease in productivity (p < 0.001). Finally, we report a gradual decrease in basal productivity (p = 0.0151) and pre-monsoon productivity (p = 0.031) in the RE. These results help us understand that changes in land use, intensive use of water, and climate can influence the ecosystem services of productivity and carbon storage offered by RE in semi-arid areas.

Assessing Riparian Vegetation Condition and Function in Disturbed Sites of the Arid Northwestern Mexico

“…Differences in EVI averages between riparian and desert habitats are consistent with other findings [8,17,35] where a higher productivity is attributed to riparian vegetation when compared to its adjacent vegetation and with the fact that water availability promotes vegetation productivity in riparian habitats [55,65,66]. Also, the seasonal difference in EVI values for desert habitat is much greater than in riparian habitat, showing that riparian habitats maintain more stable productivity rates than desert habitats, which respond drastically during the growth season when water is available through precipitation.…”

“…Based on EVI analysis, our results suggest that riparian sites with high disturbance due to human activities (which include changes in water availability, as suggested by previous studies [8,23,35] and changes in the composition and structure of vegetation) have lower photosynthetic activity (and hence productivity) than less disturbed areas.…”

Carbon Stock Estimations in a Mediterranean Riparian Forest: A Case Study Combining Field Data and UAV Imagery

“…Acacia dealbata show the highest average for the total carbon stocks (250.7 ± 89.5 tC ha −1 ), followed by Alnus glutinosa (161.6 ± 11.8 tC ha −1 ) and Salix salviifolia (73.1 ± 16.9 tC ha −1 ). Carbon reservoirs increase with forest age, successional stages and vegetation development [15]. The contrasting carbon stocks estimates found for each riparian species mainly reflect the capacity for tree growth and the biomass accumulation in the aboveground woody component, which is substantially different between Alnus glutinosa and Salix salviifolia.…”

“…Field-based estimations can be combined with GIS techniques and remote sensing approaches to obtain large-scale maps of vegetation, soil and total carbon stock distributions. Although in a very limited number, these spatial modelling approaches have been successfully applied in the USA [13,14] and Mexico [15], but also in Europe [12,16,17]. The most common methodologies rely on calibrating satellite measurements (spectral, textural and geometric variables) to in situ estimates of aboveground biomass (AGB) at field study plots.…”

“…The information is even scarcer for riparian systems located in the Mediterranean region, where estimates of AGB and carbon sequestration are extremely needed. Multispectral and hyperspectral data with high spatial resolution have been successfully used in floodplain areas to perform remote-sensing AGB-retrieval models, using in situ AGB as training and validation data [13][14][15][16]21]. However, in riparian habitats, and especially in Mediterranean regions, very high spatial resolution is mandatory to map vegetation due to the limited width and high structural complexity of riparian vegetation patches [22][23][24].…”