Tree Community Phenodynamics and Its Relationship with Climatic Conditions in a Lowland Tropical Rainforest

What drives food security for wildlife in logged and intact forests of tropical Borneo?

Timber extraction is often cited as detrimental to wildlife ecology. Little information, however, in particular from the Southeast Asian tropics, is available on how exactly logging affects wildlife food security. To address the gap, this paper presents the first high-resolution comparison of fruit production between logged and intact forests in lowland Borneo. In the period of 2004-2008, dry weight of fruit litter was assessed as a proxy for food security of wildlife. The pheno-phases of 1,054 trees in 14 sampling plots were monitored for 54 months. A total of 143,184 fruits from 50 tree families were collected from six sampling transects totalling 810 km in 34 months. Surprisingly, logged forest (mean = 23.3 kg ha^-1, SD = 48.9) produced more fruit litter than intact forest (mean = 16.7 kg ha^-1, SD = 23.3), although the difference is not significant based on Student's t test; t(66) = 0.702, p = 0.485. Pheno-phases could not be entirely explained by rainfall and temperature variables. Some evidence, however, indicates tree species composition, stand structure and sunlight exposure were likely determinants of flowering and fruit litter intensity. All things being equal, results imply selective logging if considerately practiced may increase food security for wildlife. The findings, however, should be interpreted with caution since tropical forest phenology and fruit productivity are also driven by a suite of small-scale edaphic attributes and large-scale spatio-temporal meteorological forcing. Although this research deals mainly with Borneo, the principles discussed and insights offered herein are valuable for furthering conversation around sustainable forestry in tropical Asia and elsewhere globally.

Phenological responses to climate change based on a hundred years of herbarium collections of tropical Melastomataceae

Changes in phenological events have been vastly documented in face of recent global climate change. These studies are concentrated on temperate plants, and the responses of tropical species are still little understood, likely due to the lack of long-term phenological records in the tropics. In this case, the use of herbarium specimens to gather phenological data over long periods and wide geographic areas has emerged as a powerful tool. Here, we used four Melastomataceae species endemic to the Brazilian Atlantic Forest to evaluate phenological patterns and alterations as responses to recent climate changes. Phenological data were gathered from Reflora Virtual Herbarium specimens collected between 1920 and 2018, and analyzed with circular statistics applied to the intervals 1920–1979, 1980–1999, and 2000–2018. The effects of temperature range, average temperature, precipitation, and photoperiod on flowering and fruiting of each species were tested using multiple linear regressions. Through circular statistics, we detected changes, mostly delays, in the flowering of Miconia quinquedentata, Pleroma clavatum and P. trichopodum, and in the fruiting of M. acutiflora, P. clavatum and P. trichopodum. We also found that flowering and fruiting occurrence were related to local climatic conditions from months prior to the collections. We found marked phenological variations over the decades and also that these variations are associated to global climate change, adding up to the large body of evidence from higher latitudes. Our results also support herbarium collections as an important source for long-term tropical phenological studies. The lack of consistent patterns of responses among the four species (e.g. fruiting delayed two months in P. clavatum and advanced one month in M. acutiflora) suggests that climate change has unequal effects across tropical forests. This highlights the urgent need for further research to understand and forecast the ecological implications of these changes in global ecosystems processes.