Fiber-parenchyma trade-off underlies changes in tropical forest structure and xylem architecture across a soil water gradient

Wood anatomical traits can underpin tropical forest structural and functional changes across soil water gradients and therefore could improve our mechanistic understanding of how plants adapt to environmental change. We assessed how the variation in the forest maximum height (Hmax), stem diameter, and wood density (WD) is associated with variation in xylem traits (area of fibers and parenchyma, conductive area [CondA, sum of all vessels lumens], vessel lumen area [VLA], vessel density [VD], and vessel wall reinforcement [VWR]) across 42 plots of a Brazilian Atlantic Forest habitat that span strong soil water gradients. We found that in wetter communities, greater height and lower WD were associated with greater parenchyma area (capacitance), and lower fibers, VD, VWR. Contrastingly, in drier communities, lower height was associated with higher fiber area (xylem reinforcement), WD, VD, and VWR, while parenchyma area and vessels are reduced. Tree communities vary from conservative resource-use and structurally dependent hydraulic safety (Fibers) to acquisitive resource-use and capacitance dependent hydraulic safety (parenchyma). Such a fiber-parenchyma trade-off (FPT) underlies the variation in tree height across a soil water gradient. Wood anatomy is fundamental to understanding and predicting the impacts of environmental change on forest structure.

A Study on Sensitivities of Tropical Forest GPP Responding to the Characteristics of Drought—A Case Study in Xishuangbanna, China

Droughts that occur in tropical forests (TF) are expected to significantly impact the gross primary production (GPP) and the capacity of carbon sinks. Therefore, it is crucial to evaluate and analyze the sensitivities of TF-GPP to the characteristics of drought events for understanding global climate change. In this study, the standardized precipitation index (SPI) was used to define the drought intensity. Then, the spatially explicit individual-based dynamic global vegetation model (SEIB-DGVM) was utilized to simulate the dynamic process of GPP corresponding to multi-gradient drought scenarios—rain and dry seasons × 12 level durations × 4 level intensities. The results showed that drought events in the dry season have a significantly greater impact on TF-GPP than drought events in the rainy season, especially short-duration drought events. Furthermore, the impact of drought events in the rainy season is mainly manifested in long-duration droughts. Due to abundant rainfall in the rainy season, only extreme drought events caused a significant reduction in GPP, while the lack of water in the dry season caused significant impacts due to light drought. Effective precipitation and soil moisture stock in the rainy season are the most important support for the tropical forest dry season to resist extreme drought events in the study area. Further water deficit may render the tropical forest ecosystem more sensitive to drought events.

Evaluating the utility of protected area status and conservation legislation in tropical forest conservation using satellite data: a case study of the great hornbill in Thailand

Preserving wildlife and their environment from anthropogenic activities requires identification and establishment of protected areas, and monitoring of their long-term effects on wildlife and habitat. Tropical forests are one of the most at-risk habitats and many tropical species have become extinct recently due to human activity. It is imperative to monitor habitat in protected areas and without in order to identify strategies and legislative policies that optimize conservation outcomes. To this end, I quantified habitat fragmentation for the great hornbill (Buceros bicornis) in Om Koi Wildlife Sanctuary, Thailand, pre- and post-establishment, within and outside the protected area, from 1973, 1985, and 1992, to assess the effectiveness of the protected area status, established in 1978, and a national logging ban, established in 1989, in preserving and restoring hornbill habitat. The results demonstrate that the establishment of Om Koi Wildlife Sanctuary did not decrease the rate of hornbill habitat fragmentation relative to areas outside the protected area. While the protected area had less fragmentation to begin with, protection status did not affect the rate of loss. Fragmentation increased significantly both inside and outside the protected area between the first and second time points (p < 0.05), after the protected area was first established. However, the national logging ban policy implemented in 1985 seems to have successfully halted the fragmentation of habitat within the protected area and surrounding unprotected areas, with all areas showing no significant change (p > 0.05). While not significant, the rate of fragmentation outside the protected area was greater. This suggests that the establishment of a protected area alone may not be sufficient to stop or reverse anthropogenic damage to endangered habitat and the species that utilize these environments. The incorporation of multiple strategies for management is likely needed to increase the ability of protected areas to preserve tropical forest species and habitats. The assessment of protected areas via satellite and ground-level data is an essential tool for evaluating the effectiveness of conservation strategies and improving outcomes.