Fine roots and litterfall in differing ages of riparian forest

Background/Question/Methods

Riparian forest habitat in California has been largely replaced by agriculture, due to the desirability of fertile floodplain soils for farming. However, public agencies have recently restored riparian forests on thousands of hectares along the Sacramento River. To understand how these forests are recovering over time, we established a chronosequence of 13 restoration sites ranging in age from 3 to 21 years old. Remnant forests untouched by farming or restoration efforts were included for comparison . At each site, litterfall was collected by using mesh traps laid out from June 2012 to January 2013.  Fine roots were collected by the ingrowth core method. Biomass of both litterfall and fine roots are measured for each site and plot by drying and weighing the samples.  

Results/Conclusions

Litterfall and fine root biomass differ depending on forest age, according to the results. There is a significantly lower litterfall mass in kg/hectare between forest ages 5-6 as compared to 19-21 (F_4,13=4.37, p<0.05), as well as between 5-6 compared to remnant forest (21+ yrs) (F_4,13=4.37, p<0.05).  The fine root biomass is significantly higher in the forest between ages 14-15 as compared to remnant forest (F_4,14=4.77, p<0.05). With litterfall, older forest has a significantly larger biomass than younger forest, but fine roots may have the highest biomass in the age 14-15 years, suggesting that productivity may peak at 15-20 years of age in these forests.