Male plants flower before females?

By Richard B. Primack  

 

“All good abides with him who waiteth wisely.”  Henry David Thoreau in A Week on the Concord and Merrimack Rivers. 

 

Studies using herbarium specimens are increasingly used to investigate the effects of climate change on plant phenology.  But such studies can be called into question if there are biases in how the specimens were collected.   

 

In a study of blunt-lobed spicebush in East Asia using 88 herbarium specimens and photos, it was found that male plants flowered 25 earlier on average in comparison with female plants and there was surprisingly little overlap in when they flowered.  Could male and female plants really have separate flowering times?  If so, how could they cross-pollinate and produce seeds? 

  

Specimens with male flowers were collected three weeks earlier than specimens with female flowers.

It is likely that plants with male flowers were collected preferentially during the flowering season as male flowers are more conspicuous than female flowers.  Plants with female flowers were likely sampled more frequently later in the season as female flowers are long persistent while male flowers quickly fall off. 

  

Male spicebush flowers are more conspicuous that female flowers. 

Researchers working with dioecious plants need to be aware of the biases of collectors in terms of favoring male plants during the flowering season.

Yong Yang,J. Mason Heberling, Richard B. Primack, and Benjamin R. Lee.  2022. HERBARIUM SPECIMENS MAY PROVIDE BIASED FLOWERING PHENOLOGY ESTIMATES FOR DIOECIOUS SPECIES.  International Journal of Plant Sciences. https://doi.org/10.1086/722294  

Drought affects fall foliage

By Richard Primack 

“It is pleasant to walk over the beds of these fresh, crisp, and rustling leaves. How beautifully they go to their graves!” Henry David Thoreau in Excursions. 

People in New England eagerly anticipate the beautiful autumn foliage season as leaves change from green to red, yellow, and orange. In normal years, color changes begin in late September and reach their peak in the first two weeks of October.  

 

Many leaves are just turning brown rather than changing color

This summer the persistence of severe drought conditions and high temperatures has caused the leaves of many trees and shrubs to change color early or just turn brown. The forest floor was already covered with dead brown leaves in August.  

 

The forest floor covered with dead leaves in August

 

The autumn fall foliage season is likely to be earlier than usual this year and not as dramatic. Is this a hint of how climate change will affect fall foliage in coming decades?  

 

For more details, see these two recent articles.  

 

In the Connecticut Insider: 

 

https://www.ctinsider.com/weather/article/fall-foliage-ct-2022-17389430.php

 

And in CNN: 

 

https://www.cnn.com/2022/09/10/us/fall-colors-northeast-drought-climate/index.html 

 

Was Henry David Thoreau a good naturalist?

 By Richard B. Primack

“It is not enough that we are truthful; we must cherish and carry out higher purposes to be truthful about.”  Henry David Thoreau in Early Essays and Miscellanies. 

For much of the past century-and-a-half Henry David Thoreau has been regarded as one of America’s greatest environmental philosophers. Meanwhile, his extensive observations of the natural world were largely ignored or criticized for their inaccuracy. 

An example of Thoreau’s records of plant flowering times. Primack notes are in blue.

Were Thoreau’s observations good enough for scientific use? Or were his early critics right?

In a recent article published in the journal BioScience, we present a framework for evaluating the scientific observations of historical figures using the criteria of rigor, accuracy, and utility. We apply this framework to Thoreau’s observations of flowering, leafing out, fruiting, and bird arrival times in Concord, Massachusetts. 

Not surprisingly, we find Thoreau was a good naturalist. His observations are rigorous—based on frequent and repeatable sampling. They are accurate—based on a comprehensive knowledge of species and places. And they have utility in modern ecological studies of climate change. 

The sequence of flowering of spring wildflowers that Thoreau observed is almost identical to current observations of flowering times.

This study adds to our confidence in what Thoreau has to tell us about how to observe the nature world and how we can use his observations to understand how climate change affects our world today.  

Publication: Richard Primack, Abraham Miller-Rushing, Tara K. Miller  (2022). Was Henry David Thoreau a good naturalist? An approach for assessing data from historical natural history records. BioScience.  https://doi.org/10.1093/biosci/biac063 

Plant Traits Affect Phenology

By Richard Primack 

 

“You may know what a thing costs or is worth to you; you can never know what it costs or is worth to me.” Henry David Thoreau in his Journal. 

 

The timing of events in the life of wildflowers remains under-studied despite their importance in the species richness of temperate ecosystems. To provide this information, a recent paper in the New Phytologist reports on the results of a study of 212 wildflower species at 5 botanical gardens in Germany.   

Trout lily is an early spring woodland wildflower. 

Data was collected on timing of leaf out and initial growth, flowering, fruiting, and leaf senescence.  Functional traits were also measured, including plant height, absolute and specific leaf area, leaf dry matter content, leaf carbon and nitrogen content and seed mass.  

 

Rose mallow flowers late July and August in river margins and flood plains.

Taller plants showed later timing of initial growth, and flowered, fruited and underwent leaf senescence later. Large-leaved species had shorter flowering and fruiting durations.  

Figure. Taller plants have later fruiting; blue indicates positive relationships, and red indicates negative relationships.

 

Figure. Plants with larger leaves have a shorter flowering duration.

 

There were also major differences in phenology among the five gardens, highlighting the importance of local growing conditions in affecting plant phenology.  

 

The study was published as: Sporbert, M. et al. 2022. Functional traits influence patterns in vegetative and reproductive plant phenology – a multi-botanical garden study. New Phytologist 235: 2199–2210 doi: 10.1111/nph.18345  

Drastic New England Drought

 By Selby Vaughn

“That [person] is the richest whose pleasures are the cheapest.”  Henry David Thoreau in his Journal.

New England has had a remarkably hot and dry summer, which is evident in much of the plant life throughout the Boston area. 

Coast pepperbush leaves droop as their wetland habitat dries out.

Due to the drought, many plant leaves are drooping and drying out, causing an early-onset senescence of plants which would normally take place in the autumn. 

A patch of dry, yellow, and wilting ferns. 

These drought conditions also affect fruit development, causing fruits like blueberries to shrivel up like raisins. This could lead to starvation among animals like squirrels and chipmunks that rely on these plants. 

Huckleberry plant with shrivelled fruit and dry leaves. 

The extreme high temperatures and drought we have seen within the past month may persist as climate change continues to affect our environment. While some plants may be able to withstand the drought, others may die from these extreme conditions. 

Conservation of Native Pollinators

 By Selby Vaughn

Katia Landauer, Prof. Primack and I visited conservation land at Breakneck Hill in Southborough to meet with Rob Gegear, a professor of ecology at U-Mass Dartmouth. 

Rob points out abundant native pollinators.

Rob is a huge advocate for creating more effective native pollination ecosystems, a more expansive system way of conserving native pollinators than more typical pollinator gardens. 

Rob's native pollination system.

The native pollination system which Rob has planted uses a wider diversity of native plants to encourage a wider diversity of pollinators. 

Meadowsweet, a plant favored by many native bees.

Most pollinator gardens tend to use ornamental plants and cater mainly to honeybees and common bumblebees. Rob’s garden, however, uses native plants favored by a wide variety of native pollinators, such as bee balm and shrubby St. John’s Wort. His goal is to create native pollinator systems that will increase native biodiversity and ecosystem functioning. 

Observing native pollinators in a natural environment.

Three Falls in One Park

 Richard B. Primack

“Who hears the rippling of the rivers will not utterly despair of anything.” Henry David Thoreau in his Journal.

Letchworth State Park, south of Rochester, NY, was established to protect the deep and immensely beautiful valley of the Genesee River.  The park is remarkable for having three spectacular waterfalls. The upper falls lies below an immense railroad bridge.

The upper falls

The wide middle falls lies below the historic Glen Iris Inn.

The middle falls

The Glen Iris Inn

The lower falls is in a deep gorge. Vultures and hawks circle above, riding updrafts from the gorge.

The lower falls

The steep sides of the gorge create highly varied local conditions supporting fifty tree species, making it one of the most diverse temperate forests in the world. 

Forests growing along the sides of the gorge

And yet this wonderland faces grave threats to its trees:  the emerald ash borer is killing the ash trees, and oak trees and other species are being defoliated by spongy moth caterpillars. And recently the woolly adelgid insect has arrived in the park, threatening to destroy the groves of hemlocks shading the forest paths at the top of the valley.  

Ash trees are dying due to insect attack