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Significance Forests worldwide have undergone rapid changes; however, understanding the causes of the changes has been a challenge. Climate on the regional scale has been overwhelmingly presumed to drive these changes, with little attention paid to the possible effects of competition. We compiled a long-term forest dataset from western Canada to study the relative importance of climate change and competition on tree growth, mortality, and recruitment. We showed that competition was the primary factor causing the long-term changes. Regional climate had a weaker yet significant effect on tree mortality, but no effect on tree growth and recruitment. This finding suggests that forest studies focused solely on the effects of climate may overlook the effect of other processes critical to forest dynamics. Tree mortality, growth, and recruitment are essential components of forest dynamics and resiliency, for which there is great concern as climate change progresses at high latitudes. Tree mortality has been observed to increase over the past decades in many regions, but the causes of this increase are not well understood, and we know even less about long-term changes in growth and recruitment rates. Using a dataset of long-term (1958–2009) observations on 1,680 permanent sample plots from undisturbed natural forests in western Canada, we found that tree demographic rates have changed markedly over the last five decades. We observed a widespread, significant increase in tree mortality, a significant decrease in tree growth, and a similar but weaker trend of decreasing recruitment. However, these changes varied widely across tree size, forest age, ecozones, and species. We found that competition was the primary factor causing the long-term changes in tree mortality, growth, and recruitment. Regional climate had a weaker yet still significant effect on tree mortality, but little effect on tree growth and recruitment. This finding suggests that internal community-level processes—more so than external climatic factors—are driving forest dynamics.

Synthetic aperture radar (SAR) ship detection faces significant challenges due to complex marine backgrounds, diverse ship scales and shapes, and the demand for lightweight algorithms. Traditional methods, such as constant false alarm rate and edge detection, often underperform in such scenarios. Although deep learning approaches have advanced detection capabilities, they frequently struggle to balance performance and efficiency. Algorithms of the YOLO series offer real-time detection with high efficiency, but their accuracy in intricate SAR environments remains limited. To address these issues, this paper proposes a lightweight SAR ship detection method based on the YOLOv10 framework, optimized across several key modules. The backbone network introduces a StarNet structure with multi-scale convolutional kernels, dilated convolutions, and an ECA module to enhance feature extraction and reduce computational complexity. The neck network utilizes a lightweight C2fGSConv structure, improving multi-scale feature fusion while reducing computation and parameter count. The detection head employs a dual assignment strategy and depthwise separable convolutions to minimize computational overhead. Furthermore, a hybrid loss function combining classification loss, bounding box regression loss, and focal distribution loss is designed to boost detection accuracy and robustness. Experiments on the SSDD and HRSID datasets demonstrate that the proposed method achieves superior performance, with a parameter count of 1.4 million and 5.4 billion FLOPs, and it achieves higher AP and accuracy compared to existing algorithms under various scenarios and scales. Ablation studies confirm the effectiveness of each module, and the results show that the proposed approach surpasses most current methods in both parameter efficiency and detection accuracy.

Temporal dynamics of plant-pollinator interactions inform the mechanisms of community assembly and stability. However, most studies on the dynamics of pollination networks do not consider plant reproductive traits thus offering poor understanding of the mechanism of how networks maintain stable structure under seasonal changes in flower community. We studied seasonal dynamics of pollination networks in a subtropical monsoon forest in China with a clear rainy season (April–September) and dry season (October–March) over 2 consecutive years. We constructed dioecy-ignored networks (combining visitations to dioecious male and female plants by ignoring the difference between dioecious and hermaphroditic plants) and dioecy-considered networks (excluding those visitations that only occurred either on dioecious male or female plants) for eight sampling sessions for each season. Although flower richness and flower abundance were higher in the rainy season than in the dry season, no pronounced seasonal difference was found in network specialization, nestedness and modularity for both networks. There were only significant differences in plant community robustness and pollinator specialization between seasons for dioecy-considered networks but not for dioecy-ignored networks. Furthermore, we found the flower abundance of dioecious and hermaphrodite plants mostly showed trade-off variation between rainy and dry seasons. Our results suggest various plant reproductive traits affect the temporal dynamics of pollination networks, which should be considered for conservation of plant-pollinator interactions in forest communities.

Global patterns of biodiversity reflect both regional and local processes, but the relative importance of local ecological limits to species coexistence, as influenced by the physical environment, in contrast to regional processes including species production, dispersal, and extinction, is poorly understood. Failure to distinguish regional influences from local effects has been due, in part, to sampling limitations at small scales, environmental heterogeneity within local or regional samples, and incomplete geographic sampling of species. Here, we use a global dataset comprising 47 forest plots to demonstrate significant region effects on diversity, beyond the influence of local climate, which together explain more than 92% of the global variation in local forest tree species richness. Significant region effects imply that large-scale processes shaping the regional diversity of forest trees exert influence down to the local scale, where they interact with local processes to determine the number of coexisting species.

Getting a handle on extinction rates There is broad agreement that Earth is facing a biodiversity crisis, but estimating extinction rates remains a daunting task, not least because it is almost impossible to determine when the very last individual of a species has died. Fangliang He and Stephen Hubbell demonstrate that a widely used indirect method of estimating extinction rates — based on backward extrapolation of species–area relationship data — tends to overestimate the problem. As an example, they cite data on passerine bird species in the United States. He and Hubbell stress that habitat loss remains a real and growing threat to biodiversity, although we need to develop more reliable means of monitoring the situation. Extinction from habitat loss is the signature conservation problem of the twenty-first century 1 . Despite its importance, estimating extinction rates is still highly uncertain because no proven direct methods or reliable data exist for verifying extinctions. The most widely used indirect method is to estimate extinction rates by reversing the species–area accumulation curve, extrapolating backwards to smaller areas to calculate expected species loss. Estimates of extinction rates based on this method are almost always much higher than those actually observed 2 , 3 , 4 , 5 . This discrepancy gave rise to the concept of an ‘extinction debt’, referring to species ‘committed to extinction’ owing to habitat loss and reduced population size but not yet extinct during a non-equilibrium period 6 , 7 . Here we show that the extinction debt as currently defined is largely a sampling artefact due to an unrecognized difference between the underlying sampling problems when constructing a species–area relationship (SAR) and when extrapolating species extinction from habitat loss. The key mathematical result is that the area required to remove the last individual of a species (extinction) is larger, almost always much larger, than the sample area needed to encounter the first individual of a species, irrespective of species distribution and spatial scale. We illustrate these results with data from a global network of large, mapped forest plots and ranges of passerine bird species in the continental USA; and we show that overestimation can be greater than 160%. Although we conclude that extinctions caused by habitat loss require greater loss of habitat than previously thought, our results must not lead to complacency about extinction due to habitat loss, which is a real and growing threat.

Climate change could alter plant aboveground and belowground resource allocation. Compared with shoots, we know much less about how roots, especially root system architecture (RSA) and their interactions, may respond to temperature changes. Such responses could have great influence on species'acquisition of resources and their competition with neighbors. We used a gel-based transparent growth system to observe the responses of RSA and root interactions of three common subtropical plant species seedlings in Asia differing in growth forms (herb, shrub, and tree) under a wide growth temperature range of 18-34°C, including low and supra-optimal temperatures. Results showed that the RSA, especially root depth and root width, of the three species varied significantly in response to increased temperature although the response of their aboveground shoot traits was very similar. Increased temperature was also observed to have little impact on shoot/root resource allocation pattern. The variations in RSA responses among species could lead to both the intensity and direction change of root interactions. Under high temperature, negative root interactions could be intensified and species with larger root size and fast early root expansion had competitive advantages. In summary, our findings indicate that greater root resilience play a key role in plant adapting to high temperature. The varied intensity and direction of root interactions suggest changed temperatures could alter plant competition. Seedlings with larger root size and fast early root expansion may better adapt to warmer climates.

1. The spatial pattern of tree species retains signatures of factors and processes such as dispersal, available resource patches for establishment, competition and demographics. Comparison of the spatial pattern of different size classes can thus help to reveal the importance and characteristics of the underlying processes. However, tree dynamics may be masked by large-scale heterogeneous site conditions, e.g. when the restricting size of regeneration sites superimposes emergent patterns. 2. Here we ask how environmental heterogeneity may influence the spatial dynamics of plant communities. We compared the spatial patterns and demographics of western hemlock in a homogeneous and a heterogeneous site of old-growth Douglas-fir forests on Vancouver Island using recent techniques of point pattern analysis. We used homogeneous and inhomogeneous K- and pair-correlation functions, and case-control studies to quantify the change in spatial distribution for different size classes of western hemlock. 3. Our comparative analyses show that biological processes interacted with spatial heterogeneity, leading to qualitatively different population dynamics at the two sites. Population structure, survival and size structure of western hemlock were different in the heterogeneous stand in such a way that, compared to the homogeneous stand, seedlings were more clustered, seedling densities higher, seedling mortality lower, adult growth faster and adult mortality higher. Under homogeneous site conditions, seedling survival was mainly abiotically determined by random arrival in small gaps with limiting light. At the heterogeneous site, seedling densities and initial survival were much higher, leading to strong density-dependent mortality and selection for faster growing individuals in larger size classes. We hypothesise that the dynamics of the heterogeneous stand were faster due to asymmetric competition with disproportionate benefit to taller plants. 4. Synthesis. Our study supports the hypothesis that successional dynamics are intensified in heterogeneous forest stands with strong spatial structures and outlines the importance of spatial heterogeneity as a determinant of plant population dynamics and pattern formation.

Soil plant-pathogenic (PF) and mycorrhizal fungi (MF) are both important in maintaining plant diversity, for example via host-specialized effects. However, empirical knowledge on the degree of host specificity and possible factors affecting the fungal assemblages is lacking. We identified PF and MF in fine roots of 519 individuals across 45 subtropical tree species in southern China in order to quantify the importance of host phylogeny (including via its effects on functional traits), habitat and space in determining fungal communities. We also compared host specificity in PF and MF at different host-phylogenetic scales. In both PF and MF, host phylogeny independently accounted for > 19% of the variation in fungal richness and composition, whereas environmental and spatial factors each explained no more than 4% of the variation. Over 77% of the variation explained by phylogeny was attributable to covariation in plant functional traits. Host specificity was phylogenetically scale-dependent, being stronger in PF than in MF at low host-phylogenetic scales (e.g. within genus) but similar at larger scales. Our study suggests that host-phylogenetic effects dominate the assembly of both PF and MF communities, resulting from phylogenetically clustered plant traits. The scale-dependent host specificity implies that PF were specialized at lower-level and MF at higher-level host taxa.

The rapid loss of biodiversity poses a great threat to ecosystem functions and services. Credible estimation of species extinction rates is essential for understanding the magnitude of biodiversity loss and for informing conservation, but this has been a challenge because estimated extinctions are unverifiable due to the lack of data. In this study, we investigated the relationship between local and regional extinctions and assessed the effects of range size, spatial segregation and patchiness of species distribution on this local–regional extinction relationship. We found that regional extinction rates had a convex relationship with local extinction rates, that is, the regional extinction rate was most likely to be lower than the average local rate. The regional rates deviated from local rates as the sampling area decreased. The difference between local and regional extinction rates (local–regional extinction difference) became larger if a higher number of species had larger range sizes and patchiness. We also detected that there were interactive effects among these factors. Species segregation had a weak positive relationship with the local–regional extinction difference if more species had relatively large range sizes. As the sampling areas increased, the range size showed smaller positive effects on local–regional differences, but patchiness showed larger positive effects. The local–regional extinction relationship of this study provides insights into the spatial scaling of biodiversity loss and offers some important cues for estimating regional extinctions from local data in future studies.

Tropical forests continue to be felled and fragmented around the world. A key question is how rapidly species disappear from forest fragments and how quickly humans must restore forest connectivity to minimize extinctions. We surveyed small mammals on forest islands in Chiew Larn Reservoir in Thailand 5 to 7 and 25 to 26 years after isolation and observed the near-total loss of native small mammals within 5 years from < 10-hectare (ha) fragments and within 25 years from 10- to 56-ha fragments. Based on our results, we developed an island biogeographic model and estimated mean extinction half-life (50% of resident species disappearing) to be 13.9 years. These catastrophic extinctions were probably partly driven by an invasive rat species; such biotic invasions are becoming increasingly common in human-modified landscapes. Our results are thus particularly relevant to other fragmented forest landscapes and suggest that small fragments are potentially even more vulnerable to biodiversity loss than previously thought.