Satellite‐derived estimates of forest leaf area index in southwest Western Australia are not tightly coupled to interannual variations in rainfall: implications for groundwater decline in a drying climate

Abstract

There is increasing concern that widespread forest decline could occur in regions of the world where droughts are predicted to increase in frequency and severity as a result of climate change. The average annual leaf area index (LAI) is an indicator of canopy cover and the difference between the annual maximum and minimum LAI is an indicator of annual leaf turnover. In this study, we analyzed satellite-derived estimates of monthly LAI across forested coastal catchments of southwest Western Australia over a 12 year period (2000-2011) that included the driest year on record for the last 60 years. We observed that over the 12 year study period, the spatial pattern of average annual satellite-derived LAI values was linearly related to mean annual rainfall. However, interannual changes to LAI in response to changes in annual rainfall were far less than expected from the long-term LAI-rainfall trend. This buffered response was investigated using a physiological growth model and attributed to availability of deep soil moisture and/or groundwater storage. The maintenance of high LAIs may be linked to a long-term decline in areal average underground water storage and diminished summer flows, with an emerging trend toward more ephemeral flow regimes.

Recent reduction in the frequency of frost accounts for most of the increased growth of a high elevation spruce forest in northwestern China

“…Under 1980 climatic conditions, an increase from ambient levels of CO 2 (337 ppm) to 2009 concentrations (385 ppm) was predicted to increase L from 1.95 to 2.32, equivalent to a 10 % increase in light interception by the canopy, and accounted for 50 % of the total simulated increase in P G associated with the increase in atmospheric CO 2 over the period (Table 4). The predicted increase of L is within the most sensitive range of passive remote sensing instruments (White et al 1997;Smettem et al 2013). Such a response to increasing concentrations of CO 2 is well documented (Norby et al 2005).…”

Impact of Forest Cover and Aridity on the Interplay between Effective Rooting Depth and Annual Runoff in South-West Western Australia

“…Penman potential ET was averaged for each catchment using data from Donohue et al [16]. We chose to average annual (water year runoff) from January 2000-November 2010 as it coincided with the available MODIS record and because there was no significant decline in rainfall across the study catchments over this period [29]. …”

Improving the ability of 3‐PG to model the water balance of forest plantations in contrasting environments

“…3-PG is used worldwide for different tree species such as E. globulus (Sands and Landsberg, 2002;Fontes et al, 2006;Miehle et al, 2009;Smettem et al, 2013), Eucalyptus nitens (Rodriguez et al, 2009;Pérez-Cruzado et al, 2011;Gonzalez-Garcia et al, 2015), E. grandis (Esprey et al, 2004;Stape et al, 2004;Almeida et al, 2004bAlmeida et al, , 2007, Eucalyptus cladocalyx (Paul et al, 2007), Pinus patula (Dye, 2001), Pinus radiata (Coops, 1999;Rodríguez et al, 2002;Feikema et al, 2010) and more recently to mixed species (Forrester and Tang, 2015). 3-PG is used worldwide for different tree species such as E. globulus (Sands and Landsberg, 2002;Fontes et al, 2006;Miehle et al, 2009;Smettem et al, 2013), Eucalyptus nitens (Rodriguez et al, 2009;Pérez-Cruzado et al, 2011;Gonzalez-Garcia et al, 2015), E. grandis (Esprey et al, 2004;Stape et al, 2004;Almeida et al, 2004bAlmeida et al, , 2007, Eucalyptus cladocalyx (Paul et al, 2007), Pinus patula (Dye, 2001), Pinus radiata (Coops, 1999;Rodríguez et al, 2002;Feikema et al, 2010) and more recently to mixed species (Forrester and Tang, 2015).…”