Spatial and temporal variability of fragmentation effects in a long term,eucalypt forest fragmentation experiment

Context

Although forest fragmentation is generally thought to impact tree growth and mortality negatively, recent work suggests some forests are resilient. Experimental forests provide an opportunity to examine the timing and extent of forest tree resilience to disturbance from fragmentation.

Objectives

We used the Wog Wog Habitat Fragmentation Experiment in southeastern Australia to test Eucalyptus growth and survivorship responses to forest fragmentation over a 26 year period.

Methods

We measured 2418 tree diameters and used spline-regression techniques to examine non-monotonic fragmentation effect over two time periods.

Results

Over the first 4 years after fragmentation, individual eucalypt tree growth was greater than in continuous forest for large trees and mortality rates were higher only within 10 m of edges. Over the following 22 years only the effects on tree growth remained and on average all fragments rebounded so that their biomass and mortality rates were equivalent to continuous forest. Importantly non-monotonic patterns were observed in growth and mortality with respect to area and distance from edge in both study periods, demonstrating that fragmentation impacts on trees can be strong in localized areas (greatest in 3 ha fragments and 0–30 m edges) and over short time periods.

Conclusions

Dry-sclerophyll eucalypt forests join the set of forest types that display resilient growth dynamics post fragmentation. Moreover, persistent non-monotonic impacts on tree growth with respect to tree size, fragment area, and fragment distance from edge, highlighting landscape fragmentation as a driver of habitat heterogeneity within remnant forest fragments.