Rainfall interception and redistribution by a common North American understory and pasture forb, <i>Eupatorium capillifolium</i> (Lam. dogfennel)
<p>In vegetated landscapes, rain must pass through plant canopies and litter to enter soils. As a result, some rainwater is returned to the atmosphere (i.e., interception, <span class="inline-formula"><i>I</i></span>) and the remainder is partitioned into a ca...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2020-09-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://hess.copernicus.org/articles/24/4587/2020/hess-24-4587-2020.pdf |
| Summary: | <p>In vegetated landscapes, rain must pass through plant canopies and litter to enter soils. As a result, some rainwater is returned to the atmosphere (i.e., interception, <span class="inline-formula"><i>I</i></span>) and the remainder is partitioned into a canopy (and gap) drip flux (i.e., throughfall) or drained down the stem (i.e., stemflow). Current theoretical and numerical modeling frameworks for this process are almost exclusively based on data from woody overstory plants. However, herbaceous plants often populate the understory and are the primary cover for important ecosystems (e.g., grasslands and croplands). This study investigates how overstory throughfall (<span class="inline-formula"><i>P</i><sub>T,o</sub></span>) is
partitioned into understory <span class="inline-formula"><i>I</i></span>, throughfall (<span class="inline-formula"><i>P</i><sub>T</sub></span>) and stemflow (<span class="inline-formula"><i>P</i><sub>S</sub></span>) by a dominant forb in disturbed urban forests (as well as grasslands and pasturelands), <i>Eupatorium capillifolium</i> (Lam., dogfennel). Dogfennel density at the site was 56 770 stems <span class="inline-formula">ha<sup>−1</sup></span>, enabling water storage capacities for leaves and stems of <span class="inline-formula">0.90±0.04</span> and <span class="inline-formula">0.43±0.02</span> mm, respectively. As direct measurement of <span class="inline-formula"><i>P</i><sub>T,o</sub></span> (using methods such as tipping buckets or bottles) would remove <span class="inline-formula"><i>P</i><sub>T,o</sub></span> or disturb the understory partitioning of <span class="inline-formula"><i>P</i><sub>T,o</sub></span>, overstory throughfall was modeled (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi>P</mi><mrow><mi mathvariant="normal">T</mi><mo>,</mo><mi mathvariant="normal">o</mi></mrow><mo>′</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="19pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="6e465ad308e2d99e9fc8eee8036e854e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="hess-24-4587-2020-ie00001.svg" width="19pt" height="16pt" src="hess-24-4587-2020-ie00001.png"/></svg:svg></span></span>) using on-site observations of <span class="inline-formula"><i>P</i><sub>T,o</sub></span> from a previous field campaign. Relying on modeled <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi>P</mi><mrow><mi mathvariant="normal">T</mi><mo>,</mo><mi mathvariant="normal">o</mi></mrow><mo>′</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="19pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="d9f7a5ec7c1bbf9eeded7c2e979b335a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="hess-24-4587-2020-ie00002.svg" width="19pt" height="16pt" src="hess-24-4587-2020-ie00002.png"/></svg:svg></span></span>, rather than on observations of <span class="inline-formula"><i>P</i><sub>T,o</sub></span> directly above individual plants means that significant uncertainty remains with respect to (i) small-scale relative values of <span class="inline-formula"><i>P</i><sub>T</sub></span> and <span class="inline-formula"><i>P</i><sub>S</sub></span> and (ii) factors driving <span class="inline-formula"><i>P</i><sub>S</sub></span> variability among individual dogfennel plants. Indeed, <span class="inline-formula"><i>P</i><sub>S</sub></span> data from individual plants were highly skewed, where the mean <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M20" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>P</mi><mi mathvariant="normal">S</mi></msub><mo>:</mo><msubsup><mi>P</mi><mrow><mi mathvariant="normal">T</mi><mo>,</mo><mi mathvariant="normal">o</mi></mrow><mo>′</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="38pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="99bd8c5500cf93a3291ac0bf24956780"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="hess-24-4587-2020-ie00003.svg" width="38pt" height="16pt" src="hess-24-4587-2020-ie00003.png"/></svg:svg></span></span> per plant was 36.8 %, but the median was 7.6 % (2.8 %–27.2 % interquartile range) and the total over the study period was 7.9 %. <span class="inline-formula"><i>P</i><sub>S</sub></span> variability
(<span class="inline-formula"><i>n</i>=30</span> plants) was high (CV <span class="inline-formula">></span> 200 %) and may hypothetically be explained by fine-scale spatiotemporal patterns in actual overstory throughfall (as no plant structural factors explained the variability). The total <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M24" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>P</mi><mi mathvariant="normal">T</mi></msub><mo>:</mo><msubsup><mi>P</mi><mrow><mi mathvariant="normal">T</mi><mo>,</mo><mi mathvariant="normal">o</mi></mrow><mo>′</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="38pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="eb89be15b3bf7fb8444f91fc010361e4"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="hess-24-4587-2020-ie00004.svg" width="38pt" height="16pt" src="hess-24-4587-2020-ie00004.png"/></svg:svg></span></span> was 71 % (median <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M25" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>P</mi><mi mathvariant="normal">T</mi></msub><mo>:</mo><msubsup><mi>P</mi><mrow><mi mathvariant="normal">T</mi><mo>,</mo><mi mathvariant="normal">o</mi></mrow><mo>′</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="38pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="fce5bffcf17bd5412120726041766c82"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="hess-24-4587-2020-ie00005.svg" width="38pt" height="16pt" src="hess-24-4587-2020-ie00005.png"/></svg:svg></span></span> per gauge was 72 %, with a 59 %–91 % interquartile range). Occult precipitation (mixed dew and light rain events) occurred during the study period, revealing that dogfennel can capture and drain dew to their stem base as <span class="inline-formula"><i>P</i><sub>S</sub></span>. Dew-induced <span class="inline-formula"><i>P</i><sub>S</sub></span> may help explain dogfennel's improved invasion efficacy during droughts (as it tends to be one of the most problematic weeds in the improved grazing systems in the southeastern US). Overall, dogfennel's precipitation partitioning differed markedly from the site's overstory trees (<i>Pinus palustris</i>), and a discussion of the limited literature suggests that these differences may exist across vegetated ecosystems. Thus, more research on herbaceous plant canopy interactions with precipitation is merited.</p> |
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| ISSN: | 1027-5606 1607-7938 |