The structure of old-growth forests (OGFs) is crucial for understanding the functions of forest ecosystems, environmental changes, and for formulating forest management strategies and resource conservation. However, our knowledge of the structural characteristics, dynamics, and processes of OGFs is limited. Traditional views posit that OGFs exist in a state of equilibrium; therefore, tree mortality and regeneration may exert only minor effects on their structural diversity. This study analyzed the structural diversity of a dynamic plot (120 m × 380 m) in the Knysna forest of southern South Africa over six surveys conducted between 1972 and 2007, using a set of structural parameters, namely, the uniform angle index (W), mingling (M), and dominance (U). The absolute genetic distance method was employed to test the differences in structural diversity, while Sankey diagrams were used to illustrate the flow in structural diversity over time. The results indicated that: (1) the mean values of structural parameters ranged from 0.507 to 0.512 for W, 0.817 to 0.823 for M, and 0.493 to 0.494 for U, with minor variations in their univariate, bivariate, and trivariate distributions (p > 0.05); (2) the mean values and univariate distributions of structural parameters for dead trees and renewals were close to those of the community; (3) the values for neighbors of dead trees flowed to adjacent grades for less than 50
Wildfires exert significant influences on ecosystem structure and function through modifying forest traits and environmental conditions. However, the direction and magnitude of forest phenological responses to wildfire disturbances remain insufficiently characterized. Utilizing wildfire datasets from the Global Wildfire Information System (GWIS), integrated with remote sensing phenological metrics and ancillary environmental datasets, we systematically investigated wildfire-induced alterations in photosynthetic phenology of forest ecosystems across the Northern Hemisphere during 2002–2020. Our analyses revealed that escalating burned areas and prolonged fire durations advanced the end of the growing season (EOS) of forests during the fire year, while delayed the start of the growing season (SOS) in the following year. Notably, burned area exhibited more pronounced regulatory effects on phenological shifts compared to fire duration. An increase of one standard deviation in the burned area advanced EOS by 3.24 d (P < 0.01) and delaying subsequent SOS by 5.19 d (P < 0.01). While, an increase of one standard deviation in the fire duration induced EOS advancement of 1.13 d (P < 0.01) and next SOS postponement of 2.88 d (P < 0.01). Summer wildfire incidence triggered an average EOS advancement of 6.28 d in forest post-fire seasons. Mechanistically, wildfires indirectly contributed to the shifts in EOS and subsequent SOS through increasing temperature, decreasing soil moisture and relative humidity. Above findings provide insight into how wildfire and vegetation phenology are interconnected and offering new perspectives on the challenges fire ecology and adaptive forest management in a warming climate.
While the therapeutic potential of nature exposure is well-documented, the role of forest landscape types in mediating human well-being remains underexplored. This study investigated the physio-psychological restorative effects on university students among videos of three types of forests (coniferous forest, broad-leaved forest, mixed forest), urban environment and blank control. The 177 participants underwent stress induction, then watched a 6-min video or sat still. The physiological state was assessed by heart rate (HR) and electrodermal activity (EDA), while the mental state was reflected by State-Trait Anxiety Inventory (STAI-S) and Positive Affect and Negative Affect Schedule (PANAS). The results showed that watching forest and urban video significantly reduced HR, EDA, STAI-S and negative affect (NA), while boosted the positive affect (PA). The blank control improved psychological measurements reflected in the reduction of STAI-S as well as NA and the increase of PA, but no significant effects in physiological measurements. Videos of three types of forests had better restorative effects than urban environment and blank control group both in physiological and psychological aspects, with the coniferous forest video being most effective. The study confirmed the restorative benefits of forest videos, with coniferous forest showing the strongest effects, and suggested their potential for nature-averse or time-limited individuals.
Understanding the eco-evolutionary drivers of leaf nutrient concentrations helps explain the distribution patterns of woody plants along elevation gradients in subtropical mountain forests. We measured climatic and soil properties, as well as leaf concentrations of six essential nutrients (C, N, P, K, Ca, and Mg) in woody species representing distinct plant functional groups defined by their geographic origin and leaf habit, along a subtropical mountain elevational gradient. Leaf nutrient concentrations were differentiated among plant functional groups and were phylogenetically conserved. However, evolutionary model comparisons suggest that leaf nutrient evolution along elevations was best explained by stabilizing selection towards multiple optima corresponding to different plant functional groups. Mean annual temperature (MAT) emerged as the primary environmental filter, with leaf C, N, and P concentrations showing consistent relationships with MAT across all groups, challenging a core prediction of the leaf economic spectrum theory by demonstrating convergent responses to temperature among divergent groups. In contrast, tropical-affiliated groups, particularly evergreens, displayed heightened sensitivity of leaf K, Ca, and Mg concentrations to precipitation and soil nutrient availability. Our findings thus support a novel theoretical contribution by demonstrating that leaf nutrient-based phylogenetic constraint, plant functional group differentiation, and environmental filtering operate as interdependent rather than alternative mechanisms shaping woody plant distribution along elevational gradients. We recommend that future forest management in subtropical mountain ecosystems should integrate plant functional group-specific leaf nutrient profiles into restoration and monitoring frameworks to preserve functional diversity and enhance forest resilience in the face of ongoing environmental change.
