Measuring forest health at stand level: A multi-indicator evaluation for use in adaptive management and policy

Abstract

Assessments of forest ecosystem health for use in adaptive management need an integrative multi-indicator examination at the stand scale. To assess forest health, we exained multiple forest indicators including diversity, age structure, regeneration, and edaphic factors of the dominant and associated tree species in their natural forest habitats. A stratified random cluster sampling strategy was used to gather vegetation samples from the five main forest types in the Zabarwan Mountain Range—Acacia forest (ACFT), Broad leaved forest (BLFT), Oak forest (OKFT), Pinus wallichiana forest (PWFT), and Scrub forest (SRFT). The Pearson method and canonical correspondence analysis (CCA) were used to investigate the relationship between tree species and edaphic factors. A total of 22 tree species were found, of which 13 were exotic and 9 were native. The proportion of exotic species was highest in OKFT (85%), followed by BLFT (75%), and the least (50%) SRFT. The BLFT forest type had the highest Shannon diversity while the lowest was the SRFT. ACFT and BLFT forest types have significantly higher Shannon diversity indexes than other forest types. Based on the density-girth class distribution, ACFT & SRFT forest types showed an Inverse-J distribution pattern, indicating a stable population structure. The dominant tree species, such as Populus alba in BLFT, demonstrated comparatively no regeneration, whereas Parrotiopsis jacquemontiana in SRFT, Pinus wallichiana in PWFT, Quercus robur in OKFT, and Robinia pseudoacacia demonstrated adequate regeneration performance. Overall exotic tree species such as Robinia pseudoacacia, Prunus cerasifera, Celtis australis, and Ailanthus altissima showed high/sufficient regeneration performance. The average seedling/tree value for all forest types in the area was 2.14, with the highest value at BLFT (3.61) and the lowest value at SRFT (0.71). In the CCA it showed that SRFT forests were greatly influenced by salinity and organic carbon, whereas ACFT and OKFT forests had comparable habitat preferences and were mutually influenced by electrical conductance and phosphorus availability. Prunus cerasifera was the only species positively associated with available calcium. By combining the data of numerous field-based indicators into a single integrated study, our research will give decision-makers an update on a forest's current and anticipated health.