Junqing Li

Proposed Conservation Landscape for Giant Pandas in the Minshan Mountains, China

The giant panda (Ailuropoda melanoleuca), is one of the worlds most endangered species. Habitat loss and fragmentation have reduced its numbers, shrunk its distribution, and separated the population into isolated subpopulations. Such isolated, small populations are in danger of extinction due to random demographic factors and inbreeding. We used least-cost modeling as a systematic approach to incorporate satellite imagery and data on ecological and behavioral parameters of the giant panda collected during more than 10 years of field research to design a conservation landscape for giant pandas in the Minshan Mountains. We identified 8 core habitats and 4 potential linkages that would link core habitats CH3, CH4, and CH5 with core habitats CH6, CH7, and CH8. Establishing and integrating the identified habitats with existing reserves would create an efficient reserve network for giant panda conservation. The core habitats had an average density of 4.9 pandas/100 km(2) and contained approximately 76.6% of the giant panda population. About 45% of the core habitat (3245.4 km(2)) existed outside the current nature reserves network. Total estimated core habitat decreased between 30.4 and 44.5% with the addition of residential areas and road networks factored into the model. A conservation area for giant panda in the Minshan Mountains should aim to ensure habitat retention and connectivity, improve dispersal potential of corridors, and maintain the evolutionary potential of giant pandas in the face of future environmental changes.

Climate constraints on growth and recruitment patterns of Abies faxoniana over altitudinal gradients in the Wanglang Natural Reserve, eastern Tibetan Plateau

The radial growth and recruitment patterns of trees in subalpine areas are subject to the influence of changing environmental conditions associated with changes in elevation. To investigate responses of fir radial growth and recruitment to climate factors at different elevations, tree-ring width chronologies and age structures of Abies faxoniana were developed from five sampling sites at ~2800–3300 m elevation on the north-western and south-eastern aspects in the Wanglang Natural Reserve on the eastern edge of Tibetan Plateau. Statistical characteristics of the chronologies indicated that expressed population signal and signal-to-noise ratio increased with increasing elevation in the north-western aspect; the reverse was observed on the south-eastern aspect. Correlation analysis between chronologies and climate variables showed that fir radial growth was negatively correlated with previous growing season mean temperatures and was positively correlated with January precipitation in all plots. The amount of precipitation in the growing season (June and July) greatly influenced radial growth in the two lower sites of both the aspects. The three plots on the north-western aspect were characterised by significant rates of tree recruitment in the past five decades. There were multi-decadal periods of heightened recruitment over the past three centuries in the two south-eastern plots. Widespread disturbances after 1920s were not observed in any plots and the infrequent small-scale disturbances that occurred were not the main factors influencing recent recruitment in any plots. Correlation analysis between recruitment residuals and climate variables showed that fir seedling recruitment in the north-western aspect plots was mainly controlled by spring–summer temperatures. But recruitment was greatly restricted by competition with dense bamboos and other tree species in the south-eastern aspect. Overall, previous August mean temperature and January precipitation were the dominant factors determining fir radial growth in all plots, and recruitment was sensitive to spring–summer temperatures in the plots with sparse bamboo cover.

Treeline dynamics in response to climate change in the Min Mountains, southwestern China

BackgroundAbies faxoniana is the dominant plant species of the forest ecosystem on the eastern edge of Qinghai-Tibet Plateau, where the treeline is strongly defined by climate. The tree-ring chronologies and age structure of Abies faxoniana were developed in the treeline ecotones on the northwestern and southeastern aspects of the Min Mountains in the Wanglang Nature Reserve to examine the treeline dynamics of recent decades in response to climate change.ResultsOn the northwestern aspect, correlation analysis showed that the radial growth was significantly and positively correlated with precipitation in current January and monthly mean temperature in current April, but significantly and negatively correlated with monthly mean temperature in previous August. On the southeastern aspect, the radial growth was significantly negatively correlated with monthly mean temperature in previous July and August.ConclusionsThe different responses of radial growth to climatic variability on both the aspects might be mainly due to the micro-environmental conditions. The recruitment benefited from the warm temperature in current April, July and September on the northwestern aspect. The responses of radial growth and recruitment to climatic variability were similar on the northwestern slope. Recruitment was greatly restricted by competition with dense bamboos on the southeastern aspect.

Comparing the plant diversity between artificial forest and nature growth forest in a giant panda habitat

Artificial restoration is an important way to restore forests, but little is known about its effect on the habitat restoration of the giant panda. In the present study, we investigated the characteristics of artificial forest in the Wanglang Nature Reserve to determine whether through succession it has formed a suitable habitat for the giant panda. We compared artificial forest characteristics with those of natural habitat used by the giant panda. We found that the dominant tree species in artificial forest differed from those in the natural habitat. The artificial forest had lower plant species richness and diversity in the tree and shrub layers than did the latter, and its community structure was characterized by smaller tree and bamboo sizes, and fewer and lower bamboo clumps, but more trees and larger shrub sizes. The typical community collocation of artificial forest was a “Picea asperata + no-bamboo” model, which differs starkly from the giant panda’s natural habitat. After several years of restoration, the artificial forest has failed to become a suitable habitat for the giant panda. Therefore, a simple way of planting individual trees cannot restore giant panda habitat; instead, habitat restoration should be based on the habitat requirements of the giant panda.

Comparative habitat use by takin in the Wanglang and Xiaohegou Nature Reserves

We investigated the habitat use characteristics of takin in Wanglang and Xiaohegou Nature Reserves to detect whether takin has the different habitat use patterns in different environments. We found that takin has similarities and differences in habitat use in these two nature reserves. Takin at Wanglang usually used the habitats with greater bamboo coverage and bamboo density, whereas takin at Xiaohegou usually used the habitats with a lower canopy. The results of a logistic regression analysis showed that bamboo density, herb-cover proportion, and tree size contributed significantly to the difference between takin plots at Wanglang and Xiaohegou, with an overall correct prediction rate of 92.3%, indicating that these are the main factors discriminating habitat use characteristics of takin in these two nature reserves. Considering takin has different habitat use characteristics in different areas, different protection measures should be taken to protect different takin populations. Based on the habitat use characteristics of takin at Wanglang and Xiaohegou, we summarized adaptation of takin to environments as general adaptation, regional adaptation, and special adaptation.

Resting site use of giant pandas in Wanglang Nature Reserve

Little is known about the resting sites used by the giant panda (Ailuropoda melanoleuca), which restricts our understanding of their resting habits and limits conservation efforts. To enhance our understanding of resting site requirements and factors affecting the resting time of giant pandas, we investigated the characteristics of resting sites in the Wanglang Nature Reserve, Sichuan Province, China. The results indicated that the resting sites of giant pandas were characterised by a mean slope of 21°, mean nearest tree size of 53.75 cm, mean nearest shrub size of 2.82 cm, and mean nearest bamboo number of 56. We found that the resting sites were closer to bamboo than to trees and shrubs, suggesting that the resting site use of giant pandas is closely related to the presence of bamboo. Considering that giant pandas typically rest near a large-sized tree, protection of large trees in the forests is of considerable importance for the conservation of this species. Furthermore, slope was found to be an important factor affecting the resting time of giant pandas, as they tended to rest for a relatively longer time in sites with a smaller degree of slope.

Interaction of Soil Water and Nitrogen on the Photosynthesis and Growth in Pinus tabulaeformis Seedlings

ObjectivePinus tabulaeformis is widely distributed over China, and a dominant species as an afforestation and reforestation tree species in ecological restoration and soil conservation programs. But as the climate change intensifies, P. tabulaeformis forests are experiencing soil water deficit and nitrogen deposition during growth season. Thus an experiment was carried out to investigate the interaction of different soil water content and N addition on the growth and photosynthesis of P. tabulaeformis seedlings by measuring whole-plant growth, leaf area, biomass production and allocation, leaf photosynthesis, and chlorophyll fluorescence. MethodTwo-year-old seedlings of P. tabulaeformis were subjected to a nested design with four soil water regimes (W1, W2, W3, and W4) and four N addition levels (N1, N2, N3 and N4). ResultThe result showed that N addition significantly enhanced growth and biomass production of the seedlings under plentiful soil water conditions (W3 and W4), but aggregated the negative effect of low soil water treatments (W1 and W2) on plant growth. Moreover, N addition was able to lead to an increase in photosynthetic capacity under high soil water conditions (W3 and W4), but a decrease in low soil water treatments (W1 and W2), which was paralleled with the shifts of PSII actual efficiency and PSII photochemical quenching. Furthermore, W3N2 treatment was the appropriate N supply and optimum soil water conditions to growth, biomass production, and photosynthetic capacity of P. tabulaeformis seedlings. ConclusionThese results suggest N deposition might be beneficial to biomass production and photosynthesis of P. tabulaeformis forests in the central and northeast areas in China with abundant rainfall, but harmful to P. tabulaeformis forests in the northwest arid and semi-arid regions. Thus, in the northwest arid and semi-arid regions in China, P. tabulaeformis should no longer be used as afforestation and reforestation tree species in ecological restoration and soil conservation programs.

Stomatal and Non-Stomatal Limitation to Photosynthesis in Pinus tabulaeformis Seedling under Different Soil Water Conditions:Experimental and Simulation Results

Midday depression in photosynthesis is common in plants, but the relative importance of stomatal and non-stomatal limitation to photosynthesis is variable among species. Pinus tabulaeformis is a conifer and distributed widely over China, which suggests its adaptability to a wide range of climate and soil water conditions. The aims of this study were to (a) understand the leaf gas exchange characteristics and stomatal and non-stomatal limitation of photosynthesis in P. tabulaeformis seedlings under different soil water conditions; (b) to compare the relationships between photosynthesis and stomatal conductance through simulation with three stomatal models; and (c) to determine the impact of the soil water content and the CO2 supply and demand on the simulation results. We measured diurnal variations in leaf-scale gas exchange of P. tabulaeformis seedlings grown under four soil water conditions:8% (W0), 12% (W1), 16% (W2) and 20% (W3) soil water content. There was a clear midday depression of net CO2 assimilation rate (A) and stomatal conductance (gs) in the all four soil water conditions. In the low and moderate soil water conditions (W0, W1 and W2), the midday depression in A and gs was accompanied with the decrease in intercellular CO2 concentration (Ci). However, in the high soil water condition (W3), the decreases in A and gs at midday were coupled with an increase in Ci. In addition, reduction of gs was bigger than the inhibition of A in the W0, W1 and W2. By contrast, in the W3 treatment, change in gs was in a smaller magnitude than the inhibition of A. Moreover, a high correlation between A and gs was observed across all treatments, and decrease in Ci paralleled to reductions in gs in W0, W1 and W2 treatments. However, in the W3 treatment, A and gs correlated positively with each other, and Ci remained unchanged at high gs and either increased or decreased at low gs. These results suggested that midday depression of A in W0, W1 and W2 soil water conditions was caused by closure of stomata rather than a decreased photosynthetic capacity of mesophyll cells. In contrast, midday depression in A in wet soil was controlled by non-stomatal decreases in the photosynthetic capacity of mesophyll cells. The comparison of stomatal models showed that the Medlyn model performed best in all of the four soil water conditions whether or not morning and afternoon were analysed separately. However the relationships between photosynthesis and stomatal conductance simulated by the Medlyn model differed significantly in different soil water treatments, and with morning and afternoon data separated, indicating that the Medlyn model can be improved by incorporating a function which can reflect the influence of soil moisture on the stomatal behaviour in different soil water conditions. Furthermore, it is suggested that the model simulations should be run separately in morning and afternoon for the plants that have remarkable midday depression in photosynthesis. Finally, we suggest that when both stomatal and non-stomatal limitations exist, the simulation of the relationships between photosynthesis and stomatal conductance should be operated separately, and a function, which assumes that stomatal conductance is regulated by rates of electron translation and by rates of Rubisco activity, or by the balance between the two processes, should be incorporated into the model to improve the simulation.

Effects of gap microsites and bamboo on Abies faxoniana regeneration in a subalpine forest, China

To clarify the effects of gap size and age, as well as microsites on Abies faxoniana recruitment in gaps with or without dwarf bamboo, the occurrences of A. faxoniana seedlings and saplings on four microsites were examined in a subalpine forest in Wanglang Natural Reserve, southwestern China. Results showed that: (1) while increased gap size had little effect on the seedling densities, it significantly reduced the sapling densities on moss-cover ground in A gaps (without bamboos) and those on moss-cover ground and decaying logs in AF gaps (with bamboos; P < 0.05). (2) Increased gap age also exerted little effect on the seedling densities while significantly reduced the sapling densities on decaying logs in AF gaps (P < 0.05). (3) Most of A. faxoniana seedlings and saplings occurred on decaying logs in AF gaps, but in A gaps A. faxoniana regeneration had no preference on microsites. Compared to gap characteristics, microsites are more important for A. faxoniana regeneration.