Assisted colonization of native forbs the use of climate-adjusted provenances. Sue McIntyre

Transcription

1 Assisted colonization of native forbs the use of climate-adjusted provenances Sue McIntyre

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3 Why move grassland forbs? Grassland forbs need help populations are depleted and fragmented. Climate change likely to increase the need for gene flow across landscapes. But fragmentation, small populations and low dispersal capacity prevent this. McIntyre, S. (2011) Ecological and anthropomorphic factors permitting low-risk assisted colonization in temperate grassy woodlands. Biological Conservation,144,

4 Aim of experiment Test the home site advantage hypothesis over a gradient of increased warming and drying Examine the effects of two recipient site variables: grazing exclosure and weeding Three forb species were investigated: Stackhousia monogyna, Bulbine bulbosa, Microseris lanceolata

5 Microseris lanceolata 5 cm

6 5 cm Bulbine bulbosa Age: 6 years

7 5 cm Stackhousia monogyna Age: 6 years

8 A north-west gradient from the Gundaroo receiving site warmer (1 o C), drier Source population Lithology Matching (sedimentary) Non-matching (granite) Non-matching (granite) Non-matching (granite) Relative distance from receiving site Close Close Intermediate Furthest Microseris 0.25 km 20 km 85 km 117 km Bulbine & Stackhousia 4 km 20 km 41 km 85 km

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10 Perennial grass removed, seed sown and covered with coarse sand

11 Emergence and early establishment Microseris emerged earliest and most completely in Winter. Bulbine emerged synchronously peaking in early Spring Stackhousia emerged discontinuously throughout from late Spring into the second Spring. Population effects Populations with larger seeds had higher % emergence (esp. Bulbine)

12 Weeding Hand weeded scrapes First growing season, 4 times (Sept. Jan.) Once in Sept and Sept No effects of weeding on numbers of plants at any stage in the experiment. Implications Protective effect of low fertility at site on weed impacts Site selection important

13 Numbers of plants Ungrazed Grazed Microseris - all Bulbine - all Stackhousia - all ( ) Growing season Growing season Growing season Microseris - flowering Bulbine - flowering Stackhousia - flowering n.s Season 7 values Ungrazed 0.7 (85) Grazed 0.1 (10) n.s Growing season Growing season Growing season

14 Effects of macropod grazing General effect of reducing plant numbers and numbers of flowering plants. Effects persisted over the six seasons. Kangaroos were the dominant biotic factor in terms of biomass. No evidence of excavations. Survival of inflorescences is also important e.g. in GS6: - 47% Microseris inflorescences were grazed off in the cages (insect damage), 63% in open (total n = 189). - No Stackhousia inflorescences were grazed off in the cages, 1% in open (total n = 448) - Total Bulbine numbers too small (total n = 15)

15 Microseris Suggestion of home site advantage but only in terms of flowering. Pop. 2 > 1, 3 or 4. n.s. Granite local (Pop. 2) did better thatn Pop. 1, from about 200 m away. Burst of germination and flowering followed by decline. Some suggestion of stabilization of numbers, but overall lowest success rate of the three species

16 Number of flowering plants Number of plants Number of growing seasons Pop. 1 Pop. 2 Pop. 3 Pop.4 Bulbine Hints of home site advantage. Variation in seed size had a lasting legacy (Pop. 3 small seeds) Pop. 1 Pop. 2 Flowering: Pop. 2 >1, 3, or Number of growing seasons Pop. 3 Pop. 4 Probable dormancy in GS5 due to very dry spring.

17 Number of flowering plants Number of plants Pop. 1 Pop. 2 Pop. 3 Pop. 4 Stackhousia Hints of home site advantage in terms of flowering (but n.s.) Number of growing seasons n.s. Pop. 2 lowest numbers but high rate of flowering Number of growing seasons Pop. 1 Pop. 2 Pop. 3 Pop. 4 Vegetative reproduction contributing to numbers of ramets rather than genets.

18 Species differences the hare and the slug Microseris - fast off the mark, early to reproduce (some in GS1), early to decline, but has stabilized to the smallest population. Small plants. Vulnerable to insect grazing of flowers. Bulbine the slug, seedling emergence prolific, but growth and self-thinning extremely slow, high survivorship, flowering delayed ( 3 years old), flowering % low (but increasing). Most sensitive to grazing. Small plants.

19 The slug These three Bulbine plants germinated six seasons previously. a b a b

20 and the tortoise Stackhousia slow discontinuous emergence, moderate survival, moderate onset of flowering ( 2 years old), most prolific flowerer, robust plants spreading vigorously. Trend of strongly increasing numbers of plants/ ramets and infloresences. Plants have some sensitivity to grazing.

21 What is success? Experiment viewed overall as a climate-adjusted provenancing exercise: - Microseris 331 (142 flowering) - Bulbine 1351 (15 flowering, 95 in season 7) - Stackhousia 608 (202 flowering) Plants from all populations established (smallest number was 50, Pop. 4 Microseris) % conversion of seeds to plants M = 1, B = 6, S = 2.5 Total cost of seed ($) Cost per plant 2015 ($) Total infloresences 2015 Cost per inflorescence ($) Microseris Bulbine (1.40) Stackhousia

22 Summary Seed selection No evidence of sensitivity of forbs to non-matching substrate (granite home populations did well on sedimentary soils). Home site advantage not strong. Good capacity to establish populations over a 1 O C range in average temperature. Management Weed competition can be eliminated by low fertility levels, but may result in small plants. Macropod grazing can significantly reduce plant numbers and reproduction.

23 Summary (continued) Feasibility Costs ranged from $0.10 $0.62 per established plant. Less than tube stock. No plant-raising costs, but site preparation costs. This experiment experienced average and above rainfall in the first growing season. Some proportion of seasonal failures could be expected. Site quality is often lower (high fertility, weedy) making weed competition highly significant. Macropod grazing is difficult to manage, and relevant to all establishment methods.

24 And the winner is... Stackhousia Creamy Candles