Yu‐Xuan Mo

Introduction: The applied nucleation method is a cost‐effective forest restoration strategy, but its long‐term, multi‐scale effectiveness is inadequately assessed in the tropics. Evaluating it in degraded tropical region is critical for guiding restoration. Objectives: We conducted a 20‐year study (2003–2023) of applied nucleation in a degraded tropical riparian corridor in China. We aim to quantify its effectiveness at community and landscape scales and to evaluate planted Ficus spp. as foundational species. Methods: Restoration was initiated by planting nuclei of Ficus spp. and nine other native trees. We assessed community‐scale recovery (tree diversity, functional composition, biomass) and landscape‐scale recovery (forest cover expansion, shoreline retention, connectivity) by comparing three forest types: the planted nucleation area (NA), the naturally expanded area (EA) that regenerated from NA, and a reference tropical seasonal rainforest. Results: After 20 years, restored forests (NA and EA) reached 19–30% of reference levels in tree diversity and biomass. Ficus spp. contributed 76.8% of tree biomass in NA. Species composition in restored forests was dominated by pioneer species (≥75% light‐demanding), differing from the reference forest and indicating an early successional stage. At the landscape scale, forest cover increased by 36% (+ 64 ha), natural shoreline retention rose from 38% to 90%, and connectivity increased by 119%, scoring “excellent” on China's Ecological Restoration Index. Conclusions: Applied nucleation successfully initiated a multi‐scale riparian corridor recovery. However, pioneer dominance reveals a successional bottleneck, where biodiversity recovery lags behind structural and functional recovery.

The rapid expansion of rubber monocultures over the past two decades has degraded extensive areas of tropical rainforest, raising concerns about their restoration. A key factor influencing the recovery of these forests remains their microbially mediated biogeochemical cycling processes. Here, we investigated changes in soil carbon and nutrient concentration, the carbon (C), nitrogen (N), and phosphorus (P)‐acquiring soil extracellular enzyme activities and their stoichiometric ratios (reflecting microbial nutrient limitations) following forest restoration in rubber monocultures. Furthermore, we evaluated the effects of restoration strategies (natural regeneration and restoration plantings) and soil abiotic properties on enzyme activities and examined correlations between soil nutrient concentration and enzyme activities stoichiometric ratios. Our findings revealed that the enzyme activities in restored forests differed significantly from those in rubber monocultures, with higher or lower activities depending on the enzyme types and the restoration strategies. As restoration advanced, the enzyme C:N:P became relatively balanced, indicating an alleviation of microbial C‐ and N‐limitation. Both restoration strategies alleviated microbial C‐limitation to a similar extent, but restoration plantings showed a higher alleviation of microbial N‐limitation than natural regeneration. Soil pH emerged as the main factor influencing enzyme activities. The increase in soil total P concentration significantly decreased microbial C‐limitation but increased N‐limitation. Furthermore, the increase in soil C:P and N:P ratios significantly alleviated the microbial N‐limitation. Our findings highlight that converting monoculture rubber plantations back into tropical forests through natural regeneration and restoration plantings promotes positive changes in soil microbial activity, alleviates microbial nutrient limitations, and fosters a more balanced nutrient acquisition strategy. These results provide critical scientific support for ecological restoration efforts in tropical regions.

Nitrogen (N) and phosphorus (P) resorption are assumed to be crucial for epiphyte growth in nutrient‐poor canopies, yet remain poorly understood due to unique habitats and limited access. We examined the N, P and ¹⁵N natural abundance in mature and senesced leaves of 10 vascular epiphyte species in southwest subtropical China, integrating data from a previous study in tropical lowland forest. We found that subtropical epiphytes experienced N‐limitation, likely because of the high P availability, making N relatively scarce. The mean N and P resorption efficiencies per leaf unit were 63.1% and 67.7%, with 14.7% and 12% higher than those on leaf mass, and 3.9% and 3.8% higher than those on leaf area. The combination of strategy analysis, generalized linear models and variance decomposition revealed that the N and P resorption in tropical epiphytes were combinedly regulated by stoichiometry and nutrient limitation control strategies, while subtropical epiphytes employed either the combined strategies or stoichiometry strategy alone. Notably, functional group type strongly influenced N resorption. Leaf δ¹⁵N reflected nutrient resorption with species‐specific variation, driven by functional traits. Epiphytes and terrestrial plants exhibit similar nutrient resorption patterns, which help alleviate the N and P deficiencies and support high biodiversity in forest canopies.

Societal Impact Statement: The strangler fig is known for its hemiepiphytic growth form and conspicuous strangling behavior in the tropics worldwide. It also plays an important role in providing ecological functions in tropical urban ecosystems. This study reveals strangler figs tend to colonize large trees with suitable microsites in a large tropical botanical garden and cause some negative effects on their hosts. We advocate balanced management strategies considering ecological functions, potential risks, and overall values of stranglers and their hosts. These results provide a scientific basis for us to develop better practices for plant management in urban green spaces (especially botanical gardens with high plant biodiversity) in tropical urban ecosystems.Summary: Strangler figs colonize trees in tropical cities, which contribute to a unique urban ecology and enrich local ecological functions. Understanding ecological associations between strangler figs and their host trees can improve green space management in tropical urban ecosystems. We investigated 9282 trees growing in the Xishuangbanna Tropical Botanical Garden and then analyzed the diversity, characteristics, and network of strangler figs and their host trees. We found 13 strangler fig species (319 individuals) widely colonized 67 host species, with palm hosts bearing 52% of all strangler individuals. Strangler figs had a high colonization rate in large trees with appropriate microsites (e.g., persistent palm petioles and the fork of mature trees with rough trunks). Leaf nitrogen and phosphorus content of hosts decreased significantly after strangler figs' aerial roots had entered the ground. The strangler–host network was characterized by relatively high specialization and low nestedness, and simulated management of strangler figs on large hosts and palm hosts could simplify the strangler–host network. Strangler fig colonization can be managed. Planting trees with large diameters at breast height and rough bark can increase the colonization of stranglers, while cutting off aerial roots can inhibit their establishment. The epiphytic stage is the best time to manage strangler figs. We recommend taking into consideration the trade‐offs among ecological functioning, human safety, and the multifaceted value of strangler figs and their host trees and thereby implementing comprehensive management strategies tailored to different contexts for improving green space management in the tropics.

Summary: Hemiepiphytic figs killing their host trees is an ecological process unique to the tropics. Yet the benefits and adaptive strategies of their special life history remain poorly understood. We compared leaf phosphorus (P) content data of figs and palms worldwide, and functional traits and substrate P content of hemiepiphytic figs (Ficus tinctoria), their host palm and nonhemiepiphytic conspecifics at different growth stages in a common garden. We found that leaf P content of hemiepiphytic figs and their host palms significantly decreased when they were competing for soil resources, but that of hemiepiphytic figs recovered after host death. P availability in the canopy humus and soil decreased significantly with the growth of hemiepiphytic figs. Functional trait trade‐offs of hemiepiphytic figs enabled them to adapt to the P shortage while competing with their hosts. From the common garden to a global scale, the P competition caused by high P demand of figs may be a general phenomenon. Our results suggest that P competition is an important factor causing host death, except for mechanically damaging and shading hosts. Killing hosts benefits hemiepiphytic figs by reducing interspecific P competition and better acquiring P resources in the P‐deficient tropics, thereby linking the life history strategy of hemiepiphytic figs to the widespread P shortage in tropical soils.

Understanding the stoichiometric traits of plants is critical for studying their ecological adaptation strategies. Facultative epiphytes (which can also live on the ground) are an important component of epiphytic flora of montane forest ecosystems. However, a key gap persists in our understanding how facultative epiphytes can adapt different nutritional conditions of ground and canopy habitats? To study adaptive strategies of facultative epiphytes and the characteristics of the content and stoichiometric homeostasis of C, N, and P elements, we conducted a field experiment and a greenhouse N and P additions cultivation experiment. We found that epiphytic individuals of facultative epiphytes showed lower C:N and C:P ratios, higher variation in elemental composition, and more pronounced N limitation than terrestrial individuals. Moreover, facultative epiphytes showed strong control over the elemental composition of leaves, and their stoichiometric homeostasis of leaves and stems were stronger than roots. Furthermore, the homeostasis of facultative epiphytes decreased in the order N > P. Our results indicated that epiphytic and terrestrial individuals of facultative epiphytes have difference in nutrient limitation, and they use plastic strategies in different habitats. Epiphytic individuals survive in the intermittent habitat through luxury consumption of nutrient while terrestrial individuals were relatively conservative nutrient users. Furthermore, our results implied that facultative epiphytes maintain stable metabolic leaf activity via variable element concentrations of roots to adapt to highly heterogeneous forest habitats.