Abstract: The current scale of deforestation and decline of tropical forest biodiversity stresses an important need to restore degraded tropical landscapes. Research here focuses on highly degraded pasture habitat in which tropical forest recovery may be impeded or no longer possible. Inhibition of tree recruitment in pasture habitat was investigated using four different approaches: 1) a comprehensive meta-analysis assessment of available peer-viewed data on major regeneration barriers, 2) experimental evaluation of dominant biotic or rodent-grass pasture components, 3) experimental evaluation of prevailing abiotic drought-solar radiation pasture conditions, and 4) calculation of consecutive recruitment stage transitions probabilities for overall survival probability assessment.
The use of these four different approaches illuminated on processes controlling tree recruitment in pasture habitat. The use of a meta-analysis, for example, revealed that while the overall effect of pasture habitat suppresses tree propagule abundance, some life-stages (e.g. seed removal) can be positively impacted and are associated with different life-history strategies (e.g. pioneer, persistent). On site use of an exclosure experiment, revealed that as expected aggressive pasture grasses diminish seedling establishment. An inhibitory effect driven by pasture rodents on seed-seedling abundance was also confirmed using the exclosure design. An outdoor growing experiment was similarly utilized to test if morphological traits regulated seedling survival under water and heat stress characteristic of pasture habitat. The growing experiment results did not as expected, reveal reduced survivorship under sun-dry conditions. Morphological traits that increased seedling survivorship under water and heat stress included number of leaves and root length. Lastly, estimation of recruitment stage transition probabilities found a marked regeneration bottleneck between tree seed removal to germination transitions in pasture.