merge paragraphs in Tleaf section

[teixeirak]

@NidhiVinod , please integrate the content below into a single paragraph. I'm not familiar enough with the references do so confidently. You could also move parts of the second paragraph to other paragraphs above. (Note that the second paragraph is the remains of a previous paragraph on in-situ observations, which I felt no longer made sense to keep separate.)

Vertical $T_{leaf}$ gradients are also expected to vary with canopy structure (Fig. r fig_leaf_T). Closed canopies with high LAI act as an parasol, absorbing most of the incoming radiation and preventing vertical air mixing in the understory. In contrast to closed canopies, open canopies with lower LAI allow more vertical air mixing and sunlight into the understory. This mixing and light penetration can either neutralize a $T{leaf}$ gradient or elevate $T{leaf}-T_{air}$ in the lower canopy relative to the upper canopy. The latter can result from the 'canopy greenhouse effect' or sunflecks, as mentioned above [@hardwickRelationshipLeafArea2015; @schymanskiStomatalControlLeaf2013b], and because shade leaves tend to have lower $g_s$ and greater thermal capacitance [capacity to hold heat, @schymanskiStomatalControlLeaf2013b].

In forests with dense canopies, including tropical and temperate broadleaf forests, leaves in the upper canopy experience greater $T{leaf} - T{air}$ and higher maximum $T{leaf}$ than do buffered lower-canopies, in some cases exceeding the optima for photosynthesis ($T{opt}$) because of $g_s$-limitation and high solar radiation loads [@carterExperimentalWarmingTropical2021a; @niinemetsShapeLeafPhotosynthetic1999; @doughtyAreTropicalForests2008; @fauset_differences_2018; @mauTemperateTropicalForest2018; @millerOnlySunlitLeaves2021; @rey-sanchez_spatial_2016; @rey-sanchez_spatial2016; @pauTropicalForestTemperature2018]. In contrast, in open forests with lower LAI, lower-canopy $T{leaf}$ can equal or even exceed upper canopy $T_{leaf}$, due to greater light transmission, vertical air mixing, and still air in the lower canopy and heating from the ground [Fig. r fig_NEON_verticalh, Supporting Information Figure r SIfig_NEON_allb,e, @mullerEvidenceEfficientNonevaporative2021; @martin_boundary_1999; @zweifelMiddayStomatalClosure2002; @hadleyInfluenceKrummholzMat1987]. Similarly, in very open forests or savannas, trees growing close to the ground can experience greater heat stress in their lower than upper canopies [@hadleyInfluenceKrummholzMat1987; @curtis_intracanopy_2019; @johnstonWhatLiesVertical2020].

[NidhiVinod]

I merged it here, let me know if this works

[teixeirak]

Looks great; thanks!

[NidhiVinod]

Closing this issue then!