Relationships of intra-annual stem growth with climate indicate distinct growth niches for two co-occurring temperate eucalypts

Hinko‐Najera, Nina; Umaña, Julio Carrizosa; Smith, Merryn; Löw, Markus; Griebel, Anne; Bennett, Lauren T.

doi:10.1016/j.scitotenv.2019.07.024

Cited by 6 publications

(14 citation statements)

References 88 publications

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“…Both temperature and precipitation impose limitations to growth, which is one of the key demographic process that contributes to forest AGB (Vanderwel et al 2016). Both species (Hinko‐Najera et al 2019) and ecosystem (Huang et al 2019) growth rates are highest when temperatures are at an optimum, and when other factors (such as precipitation) are not limiting. One interpretation of our analysis is that during the driest period of the year, when precipitation already imposes a constraint on growth, the effect of an additional constraint (temperature) becomes more influential.…”

Section: Discussionmentioning

confidence: 99%

Climate more important than soils for predicting forest biomass at the continental scale

et al. 2020

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Above‐ground biomass in forests is critical to the global carbon cycle as it stores and sequesters carbon from the atmosphere. Climate change will disrupt the carbon cycle hence understanding how climate and other abiotic variables determine forest biomass at broad spatial scales is important for validating and constraining Earth System models and predicting the impacts of climate change on forest carbon stores. We examined the importance of climate and soil variables to explaining above‐ground biomass distribution across the Australian continent using publicly available biomass data from 3130 mature forest sites, in 6 broad ecoregions, encompassing tropical, subtropical and temperate biomes. We used the Random Forest algorithm to test the explanatory power of 14 abiotic variables (8 climate, 6 soil) and to identify the best‐performing models based on climate‐only, soil‐only and climate plus soil. The best performing models explained ~50% of the variation (climate‐only: R2 = 0.47 ± 0.04, and climate plus soils: R2 = 0.49 ± 0.04). Mean temperature of the driest quarter was the most important climate variable, and bulk density was the most important soil variable. Climate variables were consistently more important than soil variables in combined models, and model predictive performance was not substantively improved by the inclusion of soil variables. This result was also achieved when the analysis was repeated at the ecoregion scale. Predicted forest above‐ground biomass ranged from 18 to 1066 Mg ha−1, often under‐predicting measured above‐ground biomass, which ranged from 7 to 1500 Mg ha−1. This suggested that other non‐climate, non‐edaphic variables impose a substantial influence on forest above‐ground biomass, particularly in the high biomass range. We conclude that climate is a strong predictor of above‐ground biomass at broad spatial scales and across large environmental gradients, yet to predict forest above‐ground biomass distribution under future climates, other non‐climatic factors must also be identified.

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Section: Discussionmentioning

confidence: 99%

Climate more important than soils for predicting forest biomass at the continental scale

et al. 2020

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“…BLA thus enabled us to isolate the underlying statistical relationship between GPP and Ta at the upper boundary of the distribution, thus minimizing the effect of other variables that limit GPP (like Fsd and VPD) below the boundary (Cade & Noon, 2003). Initially proposed by Webb (1972), BLA has been used to determine the Ta optima of tree stem growth (Hinko‐Najera et al, 2019), tree stomatal responses to Ta (Chambers et al, 1985), and the effect of forest edges on tree water relations (Wright et al, 2012).…”

Section: Methodsmentioning

confidence: 99%

“…to determine the Ta optima of tree stem growth (Hinko-Najera et al, 2019), tree stomatal responses to Ta (Chambers et al, 1985), and the effect of forest edges on tree water relations (Wright et al, 2012).…”

Section: Boundary-line Analysismentioning

confidence: 99%

Thermal optima of gross primary productivity are closely aligned with mean air temperatures across Australian wooded ecosystems

Bennett

Arndt

Bennett

et al. 2021

Global Change Biology

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Gross primary productivity (GPP) of wooded ecosystems (forests and savannas) is central to the global carbon cycle, comprising 67%–75% of total global terrestrial GPP. Climate change may alter this flux by increasing the frequency of temperatures beyond the thermal optimum of GPP (Topt). We examined the relationship between GPP and air temperature (Ta) in 17 wooded ecosystems dominated by a single plant functional type (broadleaf evergreen trees) occurring over a broad climatic gradient encompassing five ecoregions across Australia ranging from tropical in the north to Mediterranean and temperate in the south. We applied a novel boundary‐line analysis to eddy covariance flux observations to (a) derive ecosystem GPP–Ta relationships and Topt (including seasonal analyses for five tropical savannas); (b) quantitatively and qualitatively assess GPP–Ta relationships within and among ecoregions; (c) examine the relationship between Topt and mean daytime air temperature (MDTa) across all ecosystems; and (d) examine how down‐welling short‐wave radiation (Fsd) and vapour pressure deficit (VPD) influence the GPP–Ta relationship. GPP–Ta relationships were convex parabolas with narrow curves in tropical forests, tropical savannas (wet season), and temperate forests, and wider curves in temperate woodlands, Mediterranean woodlands, and tropical savannas (dry season). Ecosystem Topt ranged from 15℃ (temperate forest) to 32℃ (tropical savanna—wet and dry seasons). The shape of GPP–Ta curves was largely determined by daytime Ta range, MDTa, and maximum GPP with the upslope influenced by Fsd and the downslope influenced by VPD. Across all ecosystems, there was a strong positive linear relationship between Topt and MDTa (Adjusted R2: 0.81; Slope: 1.08) with Topt exceeding MDTa by >1℃ at all but two sites. We conclude that ecosystem GPP has adjusted to local MDTa within Australian broadleaf evergreen forests and that GPP is buffered against small Ta increases in the majority of these ecosystems.

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“…The responsiveness of tree productivity to changes in climate is often studied by dendrochronology, and associated measurements of tree growth rings [38,39]. However, temperate eucalypts can grow for much of the year [35,40,41] and typically lack the clear growth rings that record previous growth responses to environmental change [42]. Alternatively, long-term tree-stem growth measurements can reveal climate impacts on tree productivity, because short-term stem growth is sensitive to various climate variables [32,40,43].…”

Section: Introductionmentioning

confidence: 99%

“…However, temperate eucalypts can grow for much of the year [35,40,41] and typically lack the clear growth rings that record previous growth responses to environmental change [42]. Alternatively, long-term tree-stem growth measurements can reveal climate impacts on tree productivity, because short-term stem growth is sensitive to various climate variables [32,40,43]. For example, temperature influences stem-diameter changes, both directly through effects on cambial activity [44], and indirectly through effects on photosynthesis [45].…”

Section: Introductionmentioning

confidence: 99%

Species and Competition Interact to Influence Seasonal Stem Growth in Temperate Eucalypts

Plumanns-Pouton

Bennett

Najera-Umaña

et al. 2022

Forests

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Insights on tree species and competition effects on seasonal stem growth is critical to understanding the impacts of changing climates on tree productivity, particularly for eucalypts species that occur in narrow climatic niches and have unreliable tree rings. To improve our understanding of climate effects on forest productivity, we examined the relative importance of species, competition and climate to the seasonal stem growth of co-occurring temperate eucalypts on the tree productivity of temperate eucalypts. We measured monthly stem growth of three eucalypts (Eucalyptus obliqua, E. radiata, and E. rubida) over four years in a natural mixed-species forest in south-eastern Australia, examining the relative influences of species, competition index (CI) and climate variables on the seasonal basal area increment (BAI). Seasonal BAI varied with species and CI, and was greatest in spring and/or autumn, and lowest in summer. Our study highlights the interactive effects of species and competition on the seasonal stem growth of temperate eucalypts, clearly indicating that competitive effects are strongest when conditions are favourable to growth (spring and autumn), and least pronounced in summer, when reduced BAI was associated with less rainfall. Thus, our study indicates that management to reduce inter-tree competition would have minimal influence on stem growth during less favourable (i.e., drier) periods.

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Relationships of intra-annual stem growth with climate indicate distinct growth niches for two co-occurring temperate eucalypts

Cited by 6 publications

References 88 publications

Climate more important than soils for predicting forest biomass at the continental scale

Climate more important than soils for predicting forest biomass at the continental scale

Thermal optima of gross primary productivity are closely aligned with mean air temperatures across Australian wooded ecosystems

Species and Competition Interact to Influence Seasonal Stem Growth in Temperate Eucalypts

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