Plate Nº 60 · recorded November 13, 2026
Biology & EvolutionReported finding
Nutrient Pulses, Not Amounts, Give Invasive Plants Their Edge
In the first field test of its kind, fertiliser delivered in pulses rather than steady doses boosted two invasive plants by 66–138 percent in one growing season.
By Priya Raman3 min read666 words
In brief
- Invasive plant biomass rose by 66.1% and 137.7% under high nutrient variability in a single growing season.
- Study published in Basic and Applied Ecology by University of Tübingen and XTBG researchers.
- Eight field sites in southwestern Germany, invaded by Asian knotweed and Canada goldenrod.
- Total fertiliser input was equal across treatments; only timing differed.
- First field evidence that nutrient variability alone promotes plant invasion in natural communities.
A 66 to 138 percent surge in invasive plant growth — triggered not by extra fertiliser but by its timing — has been documented in the first field experiment of its kind. Researchers found that when the same total amount of nutrients arrives in bursts rather than steady doses, two of Europe's most problematic alien plants overwhelm their native neighbours.
The study, published in Basic and Applied Ecology, was conducted by scientists from the University of Tübingen in Germany and the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences. It offers the first field evidence that nutrient variability alone — the ebb and surge of resource supply, independent of average levels — can promote plant invasion in natural communities.
Why timing had never been tested in the field
Picture a meadow outside Tübingen in late spring, where Asian knotweed (Reynoutria bohemica) pushes through grasses that have grown there for generations. Ecologists have long suspected that fluctuating resources help invasive plants outcompete natives, but nearly all previous work relied on greenhouse pots or simplified setups. Whether the same mechanism operates in real, messy field conditions remained an open question.
The German-Chinese team answered it directly. They selected eight field sites in southwestern Germany, each already invaded by one of two alien species: Asian knotweed or Canada goldenrod (Solidago canadensis). Across the sites they established three treatments:
- Low variability: a fixed dose of fertiliser applied every week.
- High variability: double the amount of fertiliser applied every two weeks, so the total input over the season was identical in both treatments.
- Control: water only, with no added nutrients.
At the end of the growing season, the researchers harvested all aboveground biomass (the plant material growing above the soil line) and separated invasive material from native material. They then tracked how biomass and community dominance shifted under each regime.
What did the pulses do?
The results were unambiguous. Under high nutrient variability, the aboveground biomass of the two invasive species rose by 66.1 percent and 137.7 percent respectively, compared with the low-variability and control groups. That growth came with a clear increase in the invaders' dominance within the plant community.
The low-variability treatment, by contrast, produced no significant effect. Simply adding nutrients at a steady rate did not tilt the competitive balance between invasive and native species. The decisive factor was fluctuation itself.
Native communities told a different story. Total native plant biomass showed no significant change under high variability, meaning the pulses did not simply fertilise everything equally — they selectively favoured the invaders.
"To our knowledge, this is the first field evidence that increased nutrient variability alone can promote plant invasion in natural communities," said Liao Zhiyong of XTBG. "It demonstrates that fluctuating resources can alter invasion success even within a single growing season."
How do the invaders capitalise on a burst?
The mechanism aligns with a long-standing idea in invasion biology: species that can rapidly absorb and convert a sudden flush of resources gain a decisive advantage when supplies swing between scarcity and abundance. A nutrient pulse resembles a sudden downpour after drought — the plant that can drink fastest claims the water. Invasive species such as knotweed and goldenrod appear fitted to that pattern, seizing each two-week surge to build biomass that shades and squeezes their slower neighbours.
What remains uncertain?
The authors urge caution in extending the findings. The experiment covered two invasive species, one region, and a single growing season. Liao and colleagues note that further research on additional invasive species and on long-term effects is needed before scientists can predict how whole ecosystems will respond under global environmental change.
"As environmental variability continues to rise, it will be essential to identify which species and functional groups benefit from fluctuating resources," Liao added.
For land managers, the implication is practical: runoff from agriculture, urban waste and deposition does not merely raise average nutrient levels — it delivers them unevenly, and that unevenness may be the sharper edge of invasion.
via phys.org/rss-feed/ (Source)
More from Priya Raman
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Senior reporter covering people, launches and day-to-day practice in general science news at SciBeat.
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