Comparison of microhabitat selection and trace abundance of giant pandas between primary and secondary forests in Liziping Nature Reserve, China: effects of selective logging

Association between Soil Physicochemical Properties and Bacterial Community Structure in Diverse Forest Ecosystems

Although the importance of the soil bacterial community for ecosystem functions has long been recognized, there is still a limited understanding of the associations between its community composition, structure, co-occurrence patterns, and soil physicochemical properties. The objectives of the present study were to explore the association between soil physicochemical properties and the composition, diversity, co-occurrence network topological features, and assembly mechanisms of the soil bacterial community. Four typical forest types from Liziping Nature Reserve, representing evergreen coniferous forest, deciduous coniferous forest, mixed conifer-broadleaf forest, and its secondary forest, were selected for this study. The soil bacterial community was analyzed using Illumina MiSeq sequencing of 16S rRNA genes. Nonmetric multidimensional scaling was used to illustrate the clustering of different samples based on Bray-Curtis distances. The associations between soil physicochemical properties and bacterial community structure were analyzed using the Mantel test. The interactions among bacterial taxa were visualized with a co-occurrence network, and the community assembly processes were quantified using the Beta Nearest Taxon Index (Beta-NTI). The dominant bacterial phyla across all forest soils were Proteobacteria (45.17%), Acidobacteria (21.73%), Actinobacteria (8.75%), and Chloroflexi (5.06%). Chao1 estimator of richness, observed ASVs, faith-phylogenetic diversity (faith-PD) index, and community composition were distinguishing features of the examined four forest types. The first two principal components of redundancy analysis explained 41.33% of the variation in the soil bacterial community, with total soil organic carbon, soil moisture, pH, total nitrogen, carbon/nitrogen (C/N), carbon/phosphorous (C/P), and nitrogen/phosphorous (N/P) being the main soil physicochemical properties shaping soil bacterial communities. The co-occurrence network structure in the mixed forest was more complex compared to that in pure forests. The Beta-NTI indicated that the bacterial community assembly of the four examined forest types was collaboratively influenced by deterministic and stochastic ecological processes.

Giant pandas' staple food bamboo phyllosphere fungal community and its influencing factors

Giant pandas have developed a series of foraging strategies to adapt to their special bamboo diets. Although bamboo is an important food resource for giant pandas in Liziping National Nature Reserve (Liziping NR), China, there are relatively few studies on their phyllosphere fungal community and its influencing factors. Herein, we used ITS1 amplification and metagenomic sequencing to analyze the phyllosphere fungi diversity and functions (KEGG, CAZyme, and antibiotic resistance gene) and explore the influencing factors for the three giant pandas foraging bamboo species (Arundinaria spanostachya, AS; Yushania lineolate, YL; and Fargesia ferax, FF) over different seasons (spring vs. autumn) in Liziping NR, China. We found that Ascomycota and Basidiomycota were the most dominant phyla in the bamboo phyllosphere. The alpha diversity (e.g., the Sobs index and Shannon index) was relatively higher in autumn samples than in spring samples, and the community structure differed significantly between the three bamboo species in spring and autumn. Some biotic and abiotic variables (e.g., the elevation and mean base diameter of bamboo) significantly influenced the abundance, diversity, and community structure of the bamboo phyllosphere fungal community. Moreover, the functional analysis showed the differences in the glycoside hydrolase community and antibiotic resistance gene (ARG) profile between spring and autumn samples. Co-occurrence network modeling suggested that AS phyllosphere fungal communities in autumn employed a much more complex network than that in spring, and the abundance of multidrug, tetracycline, and glycopeptide resistance genes was high and closely correlated with other ARGs. These results indicate that fungal community's abundance, diversity, and community structure are mainly affected by the season, host species, and elevation. The season and host species are major factors affecting the biological functions (KEGG and CAZyme), ARGs, and interactions between sympatric bacterial and fungal communities in bamboo phyllosphere. This integrated study can provide a reference basis for the seasonal management of bamboo resources foraged by wild giant pandas, and predict the risk of antibiotic resistance in bamboo phyllosphere fungal flora in Liziping NR (Xiaoxiangling mountains), China.

Space use and microhabitat selection of wild giant pandas in Meigu Dafengding National Nature Reserve, China

The giant panda (Ailuropoda melanoleuca) is a special rare and endangered species in China and is the flagship species for global biodiversity conservation. This study used different methods including Kernel density, statistical analysis, and logistic regression analysis to investigated the spatial distribution, migration in different seasons and different distribution areas, as well as the foraging patch selection strategies of wild giant pandas in Meigu Dafengding National Nature Reserve in the Liangshan Mountains. The results demonstrated that, in the study area, giant pandas were mainly distributed in the Wahei-Yizi Yakou Habitat Corridor with an activity area of 144.93 km2, which accounted for 28.59% of the whole reserve. The core distribution area of the species was 92.07 km2 and the population density was 0.24 pcs km–2. There were two significant seasonal domains for the activities of giant pandas: the low-altitude winter habitat of Yushania maculata Yi and Yushania ailuropodina Yi bamboo species, as well as the high-altitude summer habitat of Bashania fangiana species. With seasonal changes, giant pandas migrated among different bamboo distribution regions. Giant pandas were mainly distributed in high-altitude areas that had secondary forest, tall trees with a large diameter at breast height (DBH) and bamboo forest. The spatial distribution pattern and microhabitat selection of giant pandas in Meigu Dafengding National Nature Reserve were determined. The findings of this study provide scientific implications for the local conservation and management of the habitat of wild giant pandas.

Predicting range shifts of the giant pandas under future climate and land use scenarios

Understanding and predicting how species will respond to global environmental change (i.e., climate and land use change) is essential to efficiently inform conservation and management strategies for authorities and managers. Here, we assessed the combined effect of future climate and land use change on the potential range shifts of the giant pandas (Ailuropoda melanoleuca) in Sichuan Province, China. We used species distribution models (SDMs) to forecast range shifts of the giant pandas by the 2050s and 2070s under four combined climate and land use change scenarios. We also compared the differences in distributional changes of giant pandas among the five mountains in the study area. Our SDMs exhibited good model performance and were not overfitted, with a mean Boyce index of 0.960 ± 0.015 and a mean omission rate of 0.002 ± 0.003, and suggested that precipitation seasonality, annual mean temperature, the proportion of forest cover, and total annual precipitation are the most important factors in shaping the current distribution pattern of the giant pandas. Our projections of future species distribution also suggested a range expansion under an optimistic greenhouse gas emission, while suggesting a range contraction under a pessimistic greenhouse gas emission. Moreover, we found that there is considerable variation in the projected range change patterns among the five mountains in the study area. Especially, the suitable habitat of the giant panda is predicted to increase under all scenarios in the Minshan mountains, while is predicted to decrease under all scenarios in Daxiangling and Liangshan mountains, indicating the vulnerability of the giant pandas at low latitudes. Our findings highlight the importance of an integrated approach that combines climate and land use change to predict the future species distribution and the need for a spatial explicit consideration of the projected range change patterns of target species for guiding conservation and management strategies.

Environmental Factors Influencing Phyllosphere Bacterial Communities in Giant Pandas' Staple Food Bamboos

The giant panda has developed a series of evolutionary strategies to adapt to a bamboo diet. The abundance and diversity of the phyllosphere microbiome change dramatically depending on the season, host species, location, etc., which may, in turn, affect the growth and health of host plants. However, few studies have investigated the factors that influence phyllosphere bacteria in bamboo, a staple food source of the giant panda. Amplicon sequencing of the 16S rRNA gene was used to explore the abundance and diversity of phyllosphere bacteria in three bamboo species (Arundinaria spanostachya, Yushania lineolate, and Fargesia ferax) over different seasons (spring vs. autumn), elevation, distance from water, etc., in Liziping National Nature Reserve (Liziping NR), China. And whole-genome shotgun sequencing uncovered the differences in biological functions (KEGG and Carbohydrate-Active enzymes functions) of A. spanostachya phyllosphere bacteria between spring and autumn. The results showed that the abundance and diversity of F. ferax phyllosphere bacteria were greater than that of the other two bamboo species in both seasons. And three kinds of bamboo phyllosphere bacteria in autumn were significantly higher than in spring. The season was a more important factor than host bamboo species in determining the community structure of phyllosphere bacteria based on the (un)weighted UniFrac distance matrix. The composition, diversity, and community structure of phyllosphere bacteria in bamboo were primarily affected by the season, species, altitude, tree layer, and shrub layer. Different bacterial communities perform different functions in different bamboo species, and long-term low temperatures may shape more varied and complex KEGG and Carbohydrate-Active enzymes functions in spring. Our study presented a deeper understanding of factors influencing the bacterial community in the bamboo phyllosphere. These integrated results offer an original insight into bamboo, which can provide a reference for the restoration and management of giant panda bamboo food resources in the Xiaoxiangling mountains.

A review of the impacts of four identified major human disturbances on the habitat and habitat use of wild giant pandas from 2015 to 2020

Human disturbance poses a serious threat to the survival of the giant panda (Ailuropoda melanoleuca), but few systematic and specialized reviews on the impacts of human disturbance on pandas and their habitats have been published. After the fourth giant panda survey (2011-2014), some new studies and important findings have emerged. To update the understanding of the impacts of human disturbance, research on the impacts of major human disturbances on the habitat and habitat use of wild giant pandas from 2015 to 2020 was reviewed based on 33 publications (including three books and 30 articles). The major human disturbances in panda habitat included livestock grazing, roads, herb collection, and logging. Livestock affects panda habitat by occupying, disturbing, and defecating in it, and the time and intensity of habitat use by horses are greater than the time and intensity at which pandas use their habitats. Roads affect nearby habitats by disturbing the vegetation and causing pollution, and the effect of roads extends far beyond the roads themselves and varies with road type. The impacts of logging on the forest structure and bamboo in panda habitat are long-term. Pandas avoid habitats disturbed by livestock grazing, roads, and logging. The impacts of herb collection are not known, because they have received little attention. Findings suggested a need for further research on human disturbance to giant pandas, focusing on comprehensive evaluations of the interactions between different disturbances.

Gap Analysis of Giant Panda Conservation as an Example for Planning China's National Park System

Protected areas have been the cornerstone for conservation globally [1], but gaps still exist in preserving biodiversity [2]. Meanwhile, areas designated as protected have overlaps between designations and might vary in their management [3, 4]. All three phenomena-coverage gaps, overlapping designations, and disparities in management-are present in China [5, 6]. China plans to establish a national park system for the first time, aiming to reform the existing protected-area system [7-9]. However, there has been no quantitative spatial analysis that can aid the planning of national parks. This study shows how an improved conservation gap analysis can inform the construction of new national parks. Taking the proposed Giant Panda National Park as an example, we analyzed the relationship between panda habitat and the existing protected areas, considering not only de jure designated coverage but also de facto levels of two types of potentially harmful activities (timber extraction and human disturbance). We find that, first, there are coverage gaps in the four mountains comprising the potential national park, and existing protected areas have overlaps between designations. Second, current protected areas have gaps and disparities in terms of restrictions on timber extraction and human disturbance. Third, overlapped designations and less restrictive management appear to have adverse effects on panda protection. On the basis of these results, we propose integrated management under a single national park administration, focusing on the key gaps, which we identify. This study can serve as a reference for the establishment of other national parks in China and the world.

Evaluating giant panda as a surrogate species for conservation co-occurring species in the Baishuijiang National Nature Reserve

The establishment of nature reserves is a key approach for biodiversity conservation worldwide. However, the effectiveness of nature reserves established by protecting the habitat needs of surrogate species is questioned. In this study, the Baishuijiang National Nature Reserve (Baishuijiang NNR), located in the Minshan Mountains, China, which is established mainly for the conservation of giant panda (a surrogate for the conservation of other endangered species) was selected. We quantitatively evaluated the conservation effectiveness of the reserve for giant panda and co-occurring species (here, seven protected species) using a maximum entropy model (Maxent), and analyzed spatial congruence between giant panda and other seven species. Results shown that the habitat of giant panda generally included the habitat of other seven protected species, suggesting that conservation of giant panda habitat also allows the conservation for the habitat of almost co-occurring species. Hence, the natural reserve established for giant panda as a surrogate species has a relatively high effectiveness. A high proportion of the suitable habitat for six species is inside the core zone, but a high proportion of the suitable habitat for two species is located in the experimental and buffer zones. Thus, the two species are affected by human activities. To improve the conservation effectiveness of the nature reserve, the management zones need to be amended. The result of the study will be beneficial for future conservation and management of the reserve. This study provides an effective method for evaluating the conservation effectiveness of nature reserves in other area of the worldwide.

Effects of roads on giant panda distribution: a mountain range scale evaluation

Few studies have focused on the mountain ranges scale effects of roads on wildlife. This lack of data could lead to an underestimation of the negative impact of roads on animal populations. We analyzed a dataset that included 74.4% of the giant panda population and covered 78.7% of the global giant panda habitat to estimate road-effect zones for major roads, and to investigate how these major roads influenced the distribution of giant pandas on a mountain range spatial scale. We found that the density of giant panda signs was significantly decreased by proximity to major roads. The effect zone reached 5,000 m from national roads and 1,500 m from provincial roads. Structural equation model analysis revealed that the strongest negative impact of major roads on giant pandas was via the reduction of nearby forest cover. The results should provide a better understanding of the impact of anthropogenic infrastructure and regional economic development on wildlife, thus providing a basis for conservation policy decisions. We suggest that the environmental impact assessment of proposed roadways or further researches on road ecological effects should expand to a larger scale and consider the possible habitat degradation caused by road access.

Giant panda foraging and movement patterns in response to bamboo shoot growth

Diet plays a pivotal role in dictating behavioral patterns of herbivorous animals, particularly specialist species. The giant panda (Ailuropoda melanoleuca) is well-known as a bamboo specialist. In the present study, the response of giant pandas to spatiotemporal variation of bamboo shoots was explored using field surveys and GPS collar tracking. Results show the dynamics in panda-bamboo space-time relationships that have not been previously articulated. For instance, we found a higher bamboo stump height of foraged bamboo with increasing elevation, places where pandas foraged later in spring when bamboo shoots become more fibrous and woody. The time required for shoots to reach optimum height for foraging was significantly delayed as elevation increased, a pattern which corresponded with panda elevational migration patterns beginning from the lower elevational end of Fargesia robusta distribution and gradually shifting upward until the end of the shooting season. These results indicate that giant pandas can respond to spatiotemporal variation of bamboo resources, such as available shoots. Anthropogenic interference of low-elevation F. robusta habitat should be mitigated, and conservation attention and increased monitoring should be given to F. robusta areas at the low- and mid-elevation ranges, particularly in the spring shooting season.

Changes of foraging patch selection and utilization by a giant panda after bamboo flowering

The bamboo flowering leads to the habitat fragmentation and food quality decline of a giant panda. Few empirical research has been conducted about the giant panda's response to the bamboo flowering. Here, we investigated the characteristics of bamboo stands, giant panda's activity, and selection and utilization of bamboo stands by giant panda in Taibaishan National Nature Reserve, China, over a 3-year period (September 2013-May 2016) during the Fargesia qinlingensis flowering period. Our results indicated that the proportion of whole bamboo stands flowering has gradually expanded from 26.7% in 2013 and 33.9% in 2014 to 52.3% in 2015. Although the flowering bamboo has lower crude protein and higher crude fiber than a non-flowering bamboo, the giant panda still fed on flowering bamboo from the evidence of droppings. The giant panda left its feeding sites and moved to the high elevation along river when the proportion of flowering reached 69.2% at elevation of 2350-2450 m in the third year. With the decline of the quality of bamboo stand of Fargesia qinlingensis, the giant panda abandoned its feeding sites when the threshold value of bamboo flowering reached 56.9-69.2%. Flexibility in foraging strategy and spatial behavior can help the giant panda to better adapt to the environment.

Withered on the stem: is bamboo a seasonally limiting resource for giant pandas?

In response to seasonal variation in quality and quantity of available plant biomass, herbivorous foragers may alternate among different plant resources to meet nutritional requirements. Giant pandas (Ailuropoda melanoleuca) are reliant almost exclusively on bamboo which appears omnipresent in most occupied habitat, but subtle temporal variation in bamboo quality may still govern foraging strategies, with population-level effects. In this paper, we investigated the possibility that temporal variation in the quality of this resource is involved in population regulation and examined pandas' adaptive foraging strategies in response to temporal variation in bamboo quality. Giant pandas in late winter and early spring consumed a less optimal diet in Foping Nature Reserve, as the availability of the most nutritious and preferred components and age classes of Bashania fargesii declined, suggesting that bamboo may be a seasonally limiting resource. Most panda mortalities and rescues occurred during the same period of seasonal food limitation. Our findings raised the possibility that while total bamboo biomass may not be a limiting factor, carrying capacity may be influenced by subtle seasonal variation in bamboo quality. We recommend that managers and policy-makers should consider more than just the quantity of bamboo in the understory and that carrying capacity estimates should be revised downward to reflect the fact that all bamboos are not equal.

Diet and foraging-site selection by giant pandas in a National Nature Reserve in China

For any endangered species, our understanding of the spatial variability in its diet across its distribution range, can be important for its conservation. This study focuses on the feeding habitat of the giant panda. For one full year, we surveyed seasonal foraging behaviors of giant pandas (Ailuropoda melanoleuca) in Foping Nature Reserve, China. The results indicated that giant pandas mainly foraged on new shoots ofBashania fargesiiandFargesia qinlingensisin spring and summer, and leaves constituted the major part of their diet in autumn and winter. Stems only marginally occurred in their diet in late winter and early spring. The general pattern in diet composition of giant pandas across mountains reflected the combined consequence of nutrition quality and food availability. Factors affecting foraging-site selection by giant pandas differed across seasons. In spring, they preferred foraging sites closer to trails, with new shoots ofB. fargesiihigher in basal diameter and less affected by worms. In summer, they foraged at sites with higher density of new shoots and perennial bamboos. Besides overstorey canopy, slope and distance to trails were the other two factors affecting their foraging-site selection in autumn. Temporal variation in diet composition and foraging-site selection exhibited by giant pandas perhaps reflected behaviorally adaptive strategies to changing environmental factors, helping to maximize their energy intake for successful survival and reproduction. Our results, for the first time, support the hypothesized negative effect of some worms on foraging-site selection by giant pandas due to their ingestion of new shoots in spring. Protecting of giant panda foraging sites in these areas where abundant young bamboo resource exist, strengthening management of human activities which can influence giant pandas forage to improve forage habitat quality and widely implementing actions of biological worm pest control during the period when shoot sprouts are eaten can potentially have important implications for habitat conservation for this species.