Contrasting responses to climate change at Himalayan treelines revealed by population demographics of two dominant species

Mainali, Kumar P.; Shrestha, Bharat Babu; Sharma, Ravi Kumar; Adhikari, Arjun; Gurarie, Eliezer; Singer, Michael C.; Parmesan, Camille

doi:10.1002/ece3.5968

Cited by 33 publications

(21 citation statements)

References 58 publications

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“…2a-b). While this finding could result if the colonisation success of resource acquisitive species is facilitated beyond the resource-rich lower hummock zones (Doležal et al 2019, Mainali et al 2020, this explanation does not seem to fit our results, as most plant species did not spread more outside their favoured hummock zones (Fig. 4).…”

Section: Linking Competition-faciliation Gradient To Microtopographycontrasting

confidence: 66%

Interplay of above‐ and belowground resource limitations: a competition–facilitation shift maintains species coexistence

Douda

Doudová

Holeštová

et al. 2021

Oikos

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Forest ecosystems are commonly characterised by a hierarchy of resources. During a disturbance of a forest community, increased light availability in the understorey can support competitive interactions at the expense of facilitation. This may overwhelm the role of belowground resource heterogeneity in maintaining species coexistence and so result in biotic homogenisation of a site. We re-surveyed species composition while estimating interspecific interactions along a microtopographic (moisture) gradient of a temperate swamp forest after increasing the availability of light into the undergrowth. We measured temporal changes in species diversity, compositional dissimilarity measures and functional traits, while belowground resource heterogeneity remained unchanged over time. To explain observed changes in terms of prevailing interspecific interactions, we evaluated temporal changes in the competition-facilitation balance. The productivity of understorey vegetation increased strongly over the five years of the study. This was accompanied by an increase in species diversity and the maintenance of compositional dissimilarity. The relative importance of competitive and facilitative interactions along the microtopographic gradient did not change over time. Rather than an overall biotic homogenisation of a site, we observed a spread of resource acquisitive species within the resource-rich sites and of stress-tolerant species within the resource-limited sites. We have shown that the temporary increase in productivity did not mitigate the effects of belowground resource heterogeneity on plant species turnover, which is likely maintained by contrasting interspecific interactions prevalent in different parts of the resource gradient. This suggests contrasting community assembly processes maintain diversity and productivity even in a local community.

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Section: Linking Competition-faciliation Gradient To Microtopographycontrasting

confidence: 66%

Interplay of above‐ and belowground resource limitations: a competition–facilitation shift maintains species coexistence

Douda

Doudová

Holeštová

et al. 2021

Oikos

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“…The association of older saplings (4–7 years) with tall grasses and dense P. aquilinum stands suggests this vegetation may have a protective role against browsing, perhaps associated with P. aquilinum's toxic metabolites (Barkham, 1978), and/or potential vegetative moderation of climate (Mainali et al., 2020). Sites with youngest saplings (1–3 years) were dominated by open, grazed acid grassland swards (SI Table A.4), indicating that the total absence of grazing may be unhelpful for tree recruitment (see also Morrison et al., 2019), by constraining oaks regeneration niche (Bobiec et al., 2018).…”

Section: Discussionmentioning

confidence: 99%

Optimizing opportunities for oak woodland expansion into upland pastures

Murphy

Hanley

Ellis

et al. 2022

Ecol Sol and Evidence

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Woodland expansion is widely advocated for the mitigation of climate change and its impacts. This is supported by ambitious targets for increasing tree cover in the United Kingdom and elsewhere to aid carbon storage, flood mitigation and biodiversity provision. However, it remains unclear whether natural tree establishment can supply demand for expanded treescapes in remote, anthropogenically modified upland landscapes. We assessed natural establishment of NW‐European native oak (Quercus robur, Q. petraea) saplings (< 12 years) in UK upland pasture systems adjacent to established ‘Atlantic’ oak woodlands on Dartmoor, SW England. We compared the extent of natural sapling colonization (abundance) into pasture sites on the moorland fringe and assessed their survival and growth throughout early life history using long‐ and short‐term grazing exclusion experiments. Natural oak establishment typically occurred on naturally freely draining pasture slopes and at high densities (up to 1900 saplings per ha–1) within 20 m of the nearest adult congeneric. Beyond 20 m from a likely seed source, establishment was limited with no recorded establishment between 75–100 m. The natural establishment of oak saplings in grazed pastures was specific to ontogeny with livestock exclusion only favouring the density of older recruits (8–12 years). Results suggest an age‐dependent relationship between ground cover and sapling performance; that is positive association between bare‐ground and height for 4–7 year old trees, but little effect for seedlings and younger (0–3 years) saplings. Our scoping study highlights that with informed livestock management, there is significant opportunity for natural expansion of oak woodland into upland pastures where existing propagule sources are present (woodland edge, isolated trees). We signpost, however, that rapid expansion of oak woodland into UK uplands for climate mitigation is likely to require targeted planting and temporary grazing cessation, and there is need for improved evaluation of the effects of grazer exclosure and ontogeny specific ecology to better facilitate native woodland expansion efforts.

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“…This space above treeline was completely covered by plants, mostly by ground vegetation dominated by Rhododendron anthopogon, with a fraction of it occupied by individuals of several tree species (Figure 1). The vertical distance between the treeline and the top of the mountain was >400 m. The uppermost part of this space above species limit site had no tree species, not even small saplings (additional details about the site are provided in Mainali et al, 2020).…”

Section: Study Sitementioning

confidence: 99%

“…Tree saplings establishing above treeline face a new set of environmental conditions including different amounts of radiation, longer snowpack duration at higher elevation, and different moisture regimes, soil types, and biotic interactions. For example, under the canopy of tall trees (e.g., Abies spectabilis ) below treeline in the Himalayas, ground vegetation is close to nonexistent, except in gaps (Mainali et al, 2020). Trees at or below treeline, with their open architecture, have little resistance to free atmospheric convection, resulting in tree canopy temperatures only slightly above ambient air temperatures (Körner, 2012).…”

Section: Introductionmentioning

confidence: 99%

Reciprocal transplants reveal asymmetric local adaptation of Himalayan Rhododendron approaching elevational range limit

et al. 2023

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As plant species expand their upper limits of distribution under current warming, some retain both traditional climate space and biotic environment while others encounter novel conditions. The latter is the case for Rhododendron campanulatum, a woody shrub that grows both above and below treeline at our study site in the Eastern Himalayas where a very conspicuous, stable treeline was defined by a nearly contiguous canopy of tall Abies spectabilis trees, many of which are over a century old. Prior work showed that treeline had remained static in this region while R. campanulatum expanded its elevational range limit. We tested local adaptation of R. campanulatum by performing reciprocal transplants between the species' current elevational range limit (4023 m above sea level [asl]) and just above treeline (3876 m asl). Contrary to expectation, the coldest temperatures of late winter and early mid‐spring were experienced by plants at the lower elevation: R. campanulatum at species' limit (upper site) were covered by snow for a longer period (40 more days) and escaped the coldest temperatures suffered by conspecifics at treeline (lower site). The harsher spring conditions at treeline likely explain why leaves were smaller at treeline (15.3 cm2) than at species limit (21.3 cm2). Contrary to results from equivalent studies in other regions, survival was reduced more by downslope than by upslope movement, again potentially due to extreme cold temperatures observed at treeline in spring. Upslope transplantation had no effect on mortality, but mortality of species limit saplings transplanted downslope was three times higher than that of residents at both sites. A general expectation is that locals should survive better than foreign transplants, but survival of locals and immigrants at our species limit site was identical. However, those species limit saplings that survived the transplant to treeline grew faster than both locals at treeline and the transplants at species limit. Overall, we found asymmetric adaptation: Compared with treeline saplings, those at species limit (147 m above treeline) were more tolerant of extremes in the growing season but less tolerant of extremes in winter and early mid‐spring, displaying local adaptation in a more complex manner than simply home advantage, and complicating predictions about impacts of future regional climate change.

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Contrasting responses to climate change at Himalayan treelines revealed by population demographics of two dominant species

Cited by 33 publications

References 58 publications

Interplay of above‐ and belowground resource limitations: a competition–facilitation shift maintains species coexistence

Interplay of above‐ and belowground resource limitations: a competition–facilitation shift maintains species coexistence

Optimizing opportunities for oak woodland expansion into upland pastures

Reciprocal transplants reveal asymmetric local adaptation of Himalayan Rhododendron approaching elevational range limit

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