[LTER-luq] Connection info for monthly meeting

[Sarah Stankavich]

*Hypothesis 6*. Increased frequency of intense hurricanes could result in
higher-elevation streams shifting
from consumer-controlled to producer-controlled ecosystems, due to the
increase in stream nutrient
concentrations, litter inputs, and light inputs that re-configure
terrestrial-aquatic linkages in these
headwater streams and riparian forests. (Pringle, Covich, Crowl, McDowell,
Ortiz, Ramirez)

*Background* – Twenty years of research on stream chemistry and biology
shows that there is a strong
response to hurricanes, which alter the riparian forest-stream connections,
increase some nutrients, and
change food web dynamics for months to years (Brokaw et al. 2012, Crowl et
al. 2012, McDowell et al.
2013). After hurricanes, nitrate concentrations remain elevated for 18
months or more (McDowell et al.
2013), large litter inputs enter the stream but are rapidly decomposed
(Crowl et al. 2001, Beard et al.
2005), and light levels increase because of increased canopy openness. In
many ways, the Luquillo
Mountain streams have been very resilient in response to the past two major
hurricanes.
23
Increased frequency of intense storms is likely to have profound effects on
stream communities, bidirectional
subsidy exchanges, and biogeochemistry. Shifts in riparian vegetation
toward more shade
intolerant trees will alter both the transient light regime (more frequent
periods of high light due to
repeated hurricane disturbance) as well as the baseline light regime (lower
LAI with more drought-tolerant
species), and the quality, quantity, and timing of leaf-litter inputs. We
will focus on species that are most
likely to enter or leave the riparian forest community (Hypothesis 4) and
their effects on subsidy
dynamics. Following Hurricane Hugo, we observed a 1 kg/m2 input of detrital
material across the forest
including the streams (Lodge et al. 1991). We experimentally demonstrated
that this input resulted in an
increase in dissolved C, N, and particulate C production and export (Crowl
et al. 2001).
In the longer term, we expect that our relatively unproductive communities,
limited by light and predation,
will switch from being consumer controlled to being producer controlled,
resulting in increased microbial,
algal, insect and decapod and fish densities, total biomass and secondary
production, as a consequence
of increased nutrients, allochthonous inputs, and light. In addition, the
increased inputs of coarse woody
debris and palm fronds will result in a significant increase in debris
dams, leaf-litter storage, and habitat
heterogeneity. This increased habitat complexity will most likely result in
more spatial refugia for prey
species and decreased predation by larger consumers (Macrobrachium spp)
resulting in a decrease in
top-down control on insects and smaller shrimp species. Taken in aggregate,
we hypothesize that the
increased frequency of severe storms in the LEF will fundamentally alter
the stream ecosystems,
resulting in increased primary productivity, standing stock biomass, and
tighter nutrient cycling during
extended periods between less-frequent, high-discharge events.

*Work plan* – We will enhance our existing stream monitoring to include
monthly litter inputs, light and
light gap measurements and microbial responses. In addition, nutrients,
algal standing crop as well as
insect, decapod, and fish densities and biomass will be sampled twice a
year in six headwater streams
(four of which are currently sampled as LTER focal streams; two additional
higher-elevation streams).
Sampling periods will include during the driest time of the year
(Feb-March) and the period of the most
severe storms (late September) to capture the effects of dry periods on
stream biota. Sampling methods
will follow protocols from our long term measurements (Section 3.1) and
already established within the
LUQ framework. Light gaps, coarse woody debris, and leaf-litter inputs will
be mapped and quantified in
replicate 100 m reaches in the study streams.
We will simulate hurricane impacts on the riparian vegetation using the
SORTIE and Demographics
models already parameterized for the LEF. Simulations will be used to model
both short-term (annual) as
well as long-term (decadal) impacts on riparian canopy composition and
structure. These simulation
results will guide future experimental manipulations of riparian canopy
cover and increased light on the
stream ecosystem components. Our future goals (LUQ VI) are to conduct a
canopy trimming experiment
for streams using a similar design as the CTE. We will explore the separate
and combined drought
(stream-water diversion, SDE) and hurricane disturbance through direct
manipulations and modeling.

On Wed, Feb 15, 2017 at 8:38 AM, Maria Uriarte <mu2126 at columbia.edu> wrote:

> Hi Sarah
>
> Can u pls send us hypothesis 6?
>
> Thanks Maria
>
> Sent from my iPhone
>
> On Feb 15, 2017, at 6:40 AM, Sarah Stankavich <sarahstankavich at gmail.com>
> wrote:
>
> Hi all - The monthly meeting today at 2 pm EST, 3 pm AST will focus on
> hypothesis 6. Connection info below
>
> LUQ monthly meeting
>
> Please join my meeting from your computer, tablet or smartphone.
> https://global.gotomeeting.com/join/363744021
>
> You can also dial in using your phone.
> United States: +1 (408) 650-3123 <(408)%20650-3123>
>
> Access Code: 363-744-021
>
> First GoToMeeting? Try a test session: http://help.citrix.com/getready
>
> --
> Sarah Stankavich
> LUQ-LTER Coordinator
> El Verde Field Station, Puerto Rico
> 787-764-0000 ext. 83466 <(787)%20764-0000> (office)
> 787-222-7756 <(787)%20222-7756> (cell)
>
> _______________________________________________
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>
>


-- 
Sarah Stankavich
LUQ-LTER Coordinator
El Verde Field Station, Puerto Rico
787-764-0000 ext. 83466 (office)
787-222-7756 (cell)
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