Country-level net primary production distribution and response to drought and land cover change

Root zone storage capacity (Rz) is a parameter widely used in terrestrial ecosystem models that estimate the amount of soil moisture available for transpiration. However, Rz is subject to large uncertainty, due to the lack of data on the distribution of soil properties and the depth of plant roots that actively take up water. Our study makes use of a mass-balance approach to investigate Rz in different ecosystems, and changes in water fluxes caused by land-cover change. The method needs no land-cover or soil information, and uses precipitation (P) and evapotranspiration (ET) time series to estimate the seasonal water deficit. To account for some of the uncertainty in ET, we use different methods for ET estimation, including methods based on satellite estimates, and modelling approaches that back-calculate ET from other ecosystem fluxes. We show that reduced ET due to land-cover change reduces Rz, which in turn increases baseflow in regions with a strong rainfall seasonality. This finding allows us to analyse the trade-off between gross primary production and hydrological fluxes at river basin scales. We also consider some ideas on how to use mass-balance Rz in water-stress functions as incorporated in existing terrestrial ecosystem models.

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Monitoring Effects of Land Cover Change on Biophysical Drivers in Rangelands Using Albedo

Land ◽

10.3390/land8020033 ◽

2019 ◽

Vol 8 (2) ◽

pp. 33 ◽

Cited By ~ 5

Author(s):

Zahn Münch ◽

Lesley Gibson ◽

Anthony Palmer

Keyword(s):

Land Cover ◽

Land Cover Change ◽

Carbon Storage ◽

Water Use ◽

Satellite Data ◽

Management Practices ◽

Net Primary Production ◽

Seasonal Effects ◽

Positive Trend ◽

Normalised Difference Vegetation Index

This paper explores the relationship between land cover change and albedo, recognized as a regulating ecosystems service. Trends and relationships between land cover change and surface albedo were quantified to characterise catchment water and carbon fluxes, through respectively evapotranspiration (ET) and net primary production (NPP). Moderate resolution imaging spectroradiometer (MODIS) and Landsat satellite data were used to describe trends at catchment and land cover change trajectory level. Peak season albedo was computed to reduce seasonal effects. Different trends were found depending on catchment land management practices, and satellite data used. Although not statistically significant, albedo, NPP, ET and normalised difference vegetation index (NDVI) were all correlated with rainfall. In both catchments, NPP, ET and NDVI showed a weak negative trend, while albedo showed a weak positive trend. Modelled land cover change was used to calculate future carbon storage and water use, with a decrease in catchment carbon storage and water use computed. Grassland, a dominant dormant land cover class, was targeted for land cover change by woody encroachment and afforestation, causing a decrease in albedo, while urbanisation and cultivation caused an increase in albedo. Land cover map error of fragmented transition classes and the mixed pixel effect, affected results, suggesting use of higher-resolution imagery for NPP and ET and albedo as a proxy for land cover.

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