No abstract

The relative abundance of different components of the soil food web can vary tremendously in response to plant resource inputs. However, little is known about the mechanisms that plant resource regulates the energy fluxes and soil community composition. Here, we experimentally reduced litter and root inputs for two years in China at low-, mid-, and high-latitude forests to explore the effects of plant-derived resource inputs on the nematode energy flux and community composition. Litter reduction at high and mid latitudes and root removal at low latitudes reduced nematode richness but did not alter nematode abundance. Besides, litter reduction reduced energy fluxes of bacterialfeeding nematodes at mid latitudes and energy fluxes of plant-feeding, bacterial-feeding and omnivorous-predatory nematodes at low latitudes, thus reducing the energy fluxes of total nematodes in mid-and low-latitude forests. By contrast, root removal reduced energy fluxes and relative energy flux of plant-feeding nematodes in high-and low-latitude forests. In most cases, nematode diversity in different trophic groups increased with increasing energy flux to nematodes. Taken together, our results suggest that the effects of plant resource inputs on nematode energy flux are affected by climate and plant resource type, which improves our understanding of plant-soil interactions.

Studying the dynamic characteristics, species coexistence and biodiversity conservation mechanisms of subtropical forest ecosystems is important in the study of the quantitative characteristics and spatial gap distribution patterns. Based on census data from the 20 ha dynamics plot of the subtropical evergreen broad-leaved forest in Dinghushan in 2015, we analyzed the geometric characteristics and spatial distribution pattern of gaps in the plot by combining aerial image processing technology of unmanned aerial vehicles and GIS. Results show that the gap fraction is 13.72%, the gap density is 35.75 no./ha, and the average gap area is 38.37 m 2 . Results also show that: (1) The number of gaps in the area is negatively exponentially distributed with the increase of gap area, that is, the gap is small and the marginal effect is not significant. (2) The aver-age area of forest gaps in over-mature forest stands is larger than that in mature forests, while the mature forest is more likely to have more small gaps and fewer large gaps. (3) In different habitats, the distribution of gaps in each habitat shows the same pattern as that found in the whole plot. However, the difference in the valley is significant when compared with other habitats, and gap area and gap density in the valley are larger than other habitats. The ridge gap is also distinctive, and its gap density is lower than other habitats. (4) Gap area is significantly correlated with topographic factors. It was significantly negatively correlated with altitude and convexity, and had a significantly positive correlation with aspect and gradient. Based on these comparative analyses, a monitoring system of forest canopy changes and patterns can be established using drones, to dynamically monitor forest gaps and the undergrowth community.

穿山甲(Manis pentadactyla), 国家二级重点保护动物有9种。 兽类中相对多度指数排前三的依次为野猪(Sus scrofa)、 鼬獾(Melogale moschata)和赤麂(Muntiacus vaginalis); 鸟类依次为白鹇(Lophura nycthemera)、橙头地鸫(Geokichla citrina)和紫啸鸫(Myophonus caeruleus)。 三个监测样地的相对多度指数排前三的物种基本一致, 其中鼎湖山的白鹇 相对多度指数最高; 小湘的豹猫(Prionailurus bengalensis)相对多度指数位列第三, 仅次于野猪和鼬獾; 烂柯山相 对多度指数排前三的鸟类则依次为画眉(Garrulax canorus)、灰胸竹鸡(Bambusicola thoracicus)和红嘴相思鸟

Understanding the linkages between aboveground and belowground ecosystems is important for explaining the variation in soil organisms with plant communities on a spatiotemporal scale. Here, soil nematode communities were investigated across three successional stages (early, mid, and late) in two contrasting forests at low and high latitudes in China. We found that forest succession affected the relative abundance of some nematode trophic groups, whereas it did not alter the total nematode abundance in the two forests. Nonmetric multidimensional scaling analysis showed that nematode community composition changed significantly from the early and mid‐stages to the late stage. The mantel analysis showed that total soil P at low latitude and litter C:N ratio at high latitude were more closely related to the variation in nematode community during forest succession, respectively. Total nematode diversity increased marginally with forest succession at low latitude, but first increased and then decreased with forest succession at high latitude. Interestingly, total nematode diversity was related to plant‐feeding nematode diversity during forest succession in both the forests. In addition, structural equation models showed that the diversity of different nematode trophic groups was directly affected by forest succession and indirectly affected by the quantity of soil resources and the quality of soil and litter. More importantly, forest succession drives total nematode diversity by directly affecting plant‐feeding nematode diversity. Collectively, forest succession alters the diversity and increases the dissimilarity of soil nematode communities. However, changes in soil and litter properties during forest succession at different latitudes differentially influence nematode communities.