Impact of patch size on woody tree species richness and abundance in a tropical montane evergreen forest patches of south India

We examined the effects of forest patch size on woody tree species richness and abundance in tropical montane evergreen forest patches of the Nilgiri region,south India. We sampled woody trees(>1 cm dbh) from 21 forest patches in the upper Nilgiri hills(> 2000 m elevation) and recorded a total of 35,146 individuals of 61 species, 45 genera and 30 families. Species richness and abundance of sapling/shrubs(≥ 1 to < 10 cm dbh)increased significantly with increasing patch size, but the species richness and abundance of small, medium and larger trees(≥ 10 to < 30, ≥ 30 to < 60 and ≥ 60 cm dbh,respectively) did not. Overall, forest interior species richness and abundance increased significantly with increasing patch size but edge species richness did not. Species richness and abundance of shade-tolerant and shade-demanding tree species also increased with increasing patch size. The abundance of zoochory dispersed tree species was significantly related to increasing patch size, but those dispersed by autochory did not display any clear relationship between patch size and species richness or abundance.Our findings suggest that with increasing forest patch area,tree compositional patterns may be driven by species specific shade-tolerance adaptations and dispersal patterns.Differential responses in these traits by the plant community within the individual habitat zones of forest edge and interiors likely plays a major role in determining the inherent plant community and thus the subsequent ecological processes of forest patches, including their responses to increasing patch area.

The effects of an experimental drought on the ecophysiology and fruiting phenology of a tropical rainforest palm

据预测,人为气候变化将季节性地增加平均温度和降雨。热带雨林物种将如何应对这种气候变化仍不确定。本研究分析了对澳大利亚昆士兰北部丹特里雨林的一种澳大利亚特有棕榈(Normambya normanbyi)进行4年降雨实验的影响,目的是了解模拟降雨减少对物种生理过程和果实物候的影响。我们考察了这种本地丰富的棕榈的果实物候和生理生态学特性,以确定该物种对干旱的生态响应。2015年5月,通过排涝实验,降低了约30%的土壤水分有效性。我们总共监测了8年(2009–2018年)的月度果实活性,包括排涝实验开始之前的4年。在最近几年的研究中,我们测量了干、湿两季幼嫩和成熟叶片的光合速率、气孔导度和碳稳定同位素等生理参数。研究结果表明,所有棕榈树的月度果实活性主要受光周期、平均太阳辐射和平均温度的驱动。然而,暴露于较低土壤水分的植株,其果实活性、光合速率和气孔导度均显著下降。我们还发现这些生理表现受到排涝实验、季节以及两者的相互作用的影响。2018年观察到排涝实验的棕榈的果实活力有所恢复,土壤浅层水分也有所增加(与前几年相比)。我们的研究结果表明,像N.normanbyi这样的棕榈树对未来的气候变化非常敏感,建议对其进行长期监测,以确定其对种群规模的影响。

Tree succession across a seasonally dry tropical forest and forest-savanna ecotone in northern Minas Gerais,Brazil

Aims Understanding succession in tropical forest is an important aspect of vegetation science,but to date,successional processes in sea-sonally dry tropical forests(SDtFs)have received much less atten-tion than evergreen humid tropical forests.We aim to fill this knowledge gap.Methods We investigated vegetation succession in SDtF areas consisting of three different successional stages(early,intermediate,late),and a SDtF-savanna ecotone in the municipal district of Juramento,north of Minas Gerais State,Brazil.Using twelve 400 m2 plots in each area,we compared vegetation parameters and structural variables(absolute density and basal area)and examined the floristic composition of the tree component to find gradients of change.Important Findings We found evidence of species turnover along a successional gradi-ent,with the intermediate stage showing the highest species rich-ness and diversity.this was accompanied with a significant increase in the number of tree individuals and basal area from the early to intermediate successional stage.However,the intermediate and late SDtF successional stages were more similar in structure and floristics.the ecotone was the most species rich and was similar to the intermediate SDtF and early successional stage in species richness and floristic composition respectively.these results will have implications for guiding SDtF management and recovery programs.

Organic carbon isotope and molecular fossil records of vegetation evolution in central Loess Plateau since 450 kyr

Significant uncertainties remain regarding the temporal evolution of natural vegetation during the Quaternary, and drivers of past vegetation change, on the Chinese Loess Plateau(CLP). This study presents analyses of total organic carbon isotopic composition(TOC) and n-alkane ratios(C31/C27) from the Lingtai loess-palaeosol sequence on the central CLP over the last 450 kyr. The results demonstrate that the vegetation in this region comprised a mix of C_3 and C_4 plants of herb and woody growth-form. C_3 plants dominated for most of the last 450 kyr, but this did not lead to extensive forest. C_3 woody plants were more abundant in MIS9(S3 period) and MIS5(S1 period) during warm and humid climate conditions. Herbs increased in the region since 130 kyr, possibly as a result of increased aridity. On the orbital timescales, there was a reduction of C_3 herbal plants in MIS11(S4) than in MIS12(L5), and in Holocene than in the last glacial period. Our isotope and n-alkane proxy records are in agreement with Artemisia pollen changes in the region, which is/was the dominant species in this area and varying due to different heat and water conditions between glacial and interglacial periods. Though the climate in MIS1(S0) was similar to that in MIS11(S4), a significant increase in woody plants during the Holocene suggests the impact of human activities and ecological effects of changes in fire activity.

Exploring behavioral traits over different contexts in four species of Australian funnel-web spiders

Australian funnel-web spiders are arguably the most venomous spiders in the world,with much research focusing on this aspect of their biology.However,other aspects related to their life history,ecology and behaviour have been overlooked.For the first time,we assessed repeatability.namely risk-taking behaviour,aggressiveness and activity in the contexts of predation,conspecific tolerance and exploration of a new territory in four species of Australian funnel-web spiders:two are closely related,Hadronyche valida and H.infensa,and two have overlapping distributions but occupy different habitats,H.cerberea and Atrax robustus.We also compared behaviors between species.At the species level,we found that H.valida showed consistency in risk-taking behavior when exposed to a predator stimulus,aggressiveness against conspecifics,and exploration of a new territory.In contrast,in the other species,only A.robustus showed repeatability in the context of exploration of a new territory.These results suggest that some behavioral traits are likely more flexible than others,and that the repeatability of behaviors may be species-specific in funnel-webs.When we compared species,we found differences in risk-taking behavior and defensiveness.This study provides novel insights to understanding variation in behavioral traits within and between species of funnel-web spiders,suggesting that some behavioral traits are likely context and/or species dependent,as a result of their evolutionary history.These findings provide key insights for understanding the ecological role of behavior and venom deployment in venomous animals,and a greater understanding of behavior in these medically significant and iconic spiders thatareof conservation concern.