Inconclusive Predictions and Contradictions: A Lack of Consensus on Seed Germination Response to Climate Change at High Altitude and High Latitude

Table 1

Summary of methodologies of studies subjecting alpine seeds to warming treatments. In the dataset, each combination of reference, taxa, and treatment was represented by a different row totaling 191 combinations (see methods sections for details). The final parameter summarises the impact of warming treatments using a simple description of difference in germination compared to the control by taxa; “no effect” represents a nonsignificant response () and “no measure of statistical significance” means that authors did not attempt to report the outcomes of warming treatments using analyses of means and variances.

Parameter	Categories/type of response		Unit
Reference/taxa/treatment combinations		191	Rows
Reference		9	Studies
Species		92	Taxa
Seed collection method	From plant	26	Rows
	Soil excavation	90	Rows
	Seeds purchased	3	Rows
	Not described	72	Rows
Transport (from field to experimental facility)	Ambient temperature	90	Rows
	Not described	101	Rows
Manipulation of postharvest storage conditions	Dry	150	Rows
	Cold (temperature maintained at c. 5°C)	6	Rows
	Not described	35	Rows
Postharvest storage time	2 days	27	Rows
	1 week	5	Rows
	2 weeks	46	Rows
	2 h–3 wk	6	Rows
	6 weeks	90	Rows
	Not described	17	Rows
Postharvest storage temperature	Room temperature	51	Rows
	5°C	6	Rows
	15°C	90	Rows
	Not described	44	Rows
Light conditions during postharvest storage	Dark	6	Rows
	Not described	185	Rows
Dormancy breaking treatment	Cold-stratification (given under snow cover and different temperature equated to winter conditions and collected after overwintering)	137	Rows
	Assumed to be stratified during postharvest storage	9	Rows
	Cold-stratification plus gibberellic acid	45	Rows
Cold-stratification duration	4 weeks	5	Rows
	12 weeks	3	Rows
	20 weeks	46	Rows
	32 weeks/8 months	12	Rows
	34 weeks	6	Rows
	39 weeks	16	Rows
	10 months	90	Rows
	Not applicable	1	Rows
	Not described	12	Rows
Cold-stratification temperature	0.5°C	26	Rows
	−7 to 0°C	16	Rows
	1–12 wks at 21/15°C, 12–32 wks at 0.5°C	3	Rows
	20 weeks at 2°C, 12 weeks warm stratification	1	Rows
	Beneath snow for approximately 24 weeks and then stored at 2°C	8	Rows
	1–4 wks (0.5°C), 5–8 wks (−5°C), 9–12 wks (−10°C), 13–16 wks (−5°C), and 17–20 wks (0.5°C)	23	Rows
	−20°C	5	Rows
	Field conditions	96	Rows
	Not applicable	1	Rows
	Not described	12	Rows
Light conditions during cold-stratification	Dark	84	Rows
	Natural conditions at midlatitudes	90	Rows
	Not described	5	Rows
	Not applicable	12	Rows
Stage at which temperature increase was imposed	Seed maturation	5	Rows
	Dormancy breaking	46	Rows
	Germination	124	Rows
	Both (dormancy breaking and germination)	16	Rows
Temperature increase compared to control conditions (°C)	1–3°C	5	Rows
	1	2	Rows
	2.4°C	8	Rows
	2.5°C	46	Rows
	2°C	3	Rows
	3°C	11	Rows
	4°C	101	Rows
	6–10°C	6	Rows
	8°C	3	Rows
	5/0°C	2	Rows
	10/4°C	2	Rows
	15/9°C	2	Rows
Germination medium	Agar	16	Rows
	Excavated soil	101	Rows
	Commercial soil	46	Rows
	Filter paper	11	Rows
	Sown in field	2	Rows
	Sown in field (removed natural soil and used commercial soil)	9	Rows
	Soil + perlite	6	Rows
Light conditions during germination	Natural + additional 4 hrs illumination during winter	90	Rows
	Natural	11	Rows
	24 h light	5	Rows
	Simulated field conditions	85	Rows
Length of germination/seedling monitoring time	35 days	5	Rows
	8 weeks	8	Rows
	12 weeks	6	Rows
	13 weeks	57	Rows
	16 weeks	8	Rows
	24 weeks	6	Rows
	30 weeks	90	Rows
	1 year	9	Rows
	4 years	2	Rows
Postgermination viability tests	Embryo inspection	3	Rows
	Not described	188	Rows
Overall effect of warming on proportion/number of seeds germinating	Increase	31	Rows
	Decrease	19	Rows
	No effect	51	Rows
	No measure of statistical significance	90	Rows

Row used here describes a species entered with all its details including seed collection, transport, postharvest storage, postharvest storage conditions, postharvest storage duration, dormancy breaking, cold-stratification conditions, cold-stratification duration, and germination conditions. In the case of same species treated with different conditions, multiple entries were made. Thus, a species can be represented by more than one row. Each unit given as row indicates how many rows correspond to each category. Thus, each unit given as row indicates a particular set of treatment-taxa combination.
Graae et al. [27] storedseeds of Cerastium alpinum L. ssp. lanatum (Lam.) Asch. and Graebn, Polygonum viviparum L., and Saxifraga cernua L. at room temperature in paper bags in dry state. But the moisture content of the seeds was not given. They assumed the seeds do not require any further stratification to germinate.
Müller et al. [58] collected soil core containing seeds roughly about 10 months after the seeds had dispersed. They handled the seeds by splitting them in to two groups: (1) one receiving gibberellic acid treatment after 10 months in soil, presumably cold-stratified in the field (45 cases); (2) one receiving no gibberellic acid treatment meaning the seeds had just undergone cold-stratification (45 cases). Please note that since both the groups underwent cold-stratification, data reporting cold-stratification time and duration (in subsequent rows) describes the cold-stratification time and duration even in gibberellic acid treated seeds.
Some studies only applied warming during germination phase or cold-stratification stage. Few studies applied warming during both cold-stratification and germination phases.