title: Global beta-diversity of angiosperm trees is shaped by Quaternary climate change

authors: Xu, W-B

subjects: Humans

abstract: As Earth's climate has varied strongly through geological time, studying the impacts of past climate change on biodiversity helps to understand the risks from future climate change. However, it remains unclear how paleoclimate shapes spatial variation in biodiversity. Here, we assessed the influence of Quaternary climate change on spatial dissimilarity in taxonomic, phylogenetic, and functional composition among neighboring 200-kilometer cells (beta-diversity) for angiosperm trees worldwide. We found that larger glacial-interglacial temperature change was strongly associated with lower spatial turnover (species replacements) and higher nestedness (richness changes) components of beta-diversity across all three biodiversity facets. Moreover, phylogenetic and functional turnover was lower and nestedness higher than random expectations based on taxonomic beta-diversity in regions that experienced large temperature change, reflecting phylogenetically and functionally selective processes in species replacement, extinction, and colonization during glacial-interglacial oscillations. Our results suggest that future human-driven climate change could cause local homogenization and reduction in taxonomic, phylogenetic, and functional diversity of angiosperm trees worldwide.

text: Global beta-diversity of angiosperm trees is shaped by Quaternary climate change As Earth's climate has varied strongly through geological time, studying the impacts of past climate change on biodiversity helps to understand the risks from future climate change. However, it remains unclear how paleoclimate shapes spatial variation in biodiversity. Here, we assessed the influence of Quaternary climate change on spatial dissimilarity in taxonomic, phylogenetic, and functional composition among neighboring 200-kilometer cells (beta-diversity) for angiosperm trees worldwide. We found that larger glacial-interglacial temperature change was strongly associated with lower spatial turnover (species replacements) and higher nestedness (richness changes) components of beta-diversity across all three biodiversity facets. Moreover, phylogenetic and functional turnover was lower and nestedness higher than random expectations based on taxonomic beta-diversity in regions that experienced large temperature change, reflecting phylogenetically and functionally selective processes in species replacement, extinction, and colonization during glacial-interglacial oscillations. Our results suggest that future human-driven climate change could cause local homogenization and reduction in taxonomic, phylogenetic, and functional diversity of angiosperm trees worldwide.

year: 2023-04-05

title: Oceanographic and morphodynamic monitoring of a multi-purpose reef at Mount Maunganui, New Zealand

authors: Weppe, Simon Bastien

subjects: multi-purpose reef

abstract: The innovative concept of an offshore submerged multi-purpose reef combining a
coastal protection function with recreational benefits including improved surfing,
diving, or fishing conditions provides an appealing solution for the management
of beaches. However, since the technology is relatively recent, there is still a lack
of empirical knowledge about its performance in the field. The present research
monitored the effect of the prototype  research  reef constructed at Mount
Maunganui in New Zealand on the local beach morphodynamics and
oceanographic conditions, being primarily concerned with implications on the
coastal protection function of the technology.
The beach morphodynamic response to the reef was investigated from a set of
already available high resolution bathymetric surveys imaging the foreshore and
surfzone morphology prior to, and throughout reef construction, and a new postconstruction
survey collected as a part of this research. The reef implementation
was found to disturb the pre-existing beach state functioning including the
onshore/offshore migration of the underlying long shore bar, rather than cause a
persistent salient response. A possible additional beach width of ~ 20 m,
extending ~ 150 m alongshore was identified in the lee of the reef from shoreline
analysis, but the pattern was transient throughout the monitoring period since it
was superimposed on comparatively large pre-existing fluctuations. In addition,
the reef structure provided a control point on the offshore morphology able to trap
sediment updrift and erode sediment downdrift.
Both field measurements and numerical modelling of waves and currents were
used to monitor the effect of the reef on the oceanographic conditions. Wave
propagation over the reef without breaking (H less than 0.5 m) resulted in transmitted
heights larger than incident by up to a factor of 2. When the reef triggered
breaking, transmitted heights were reduced by up to ~40 %. A concurrent process
was the shift of the wave energy spectra towards higher frequencies landward of
the reef that resulted in reduced transmitted wave periods. Wave modelling
showed that the wave shadowing was associated with significant wave rotation
around the reef that induced two zones of divergent wave angles near the
shoreline in the lee of the reef. The hydrodynamic response to the wave energy
dissipation was the development of stronger onshore directed currents landward of
the reef. Hydrodynamic modelling indicated that the reef-induced flow forced a
cellular circulation in the lee side under shore normal waves, and an onshore
deviation of the ambient (unidirectional) long-shore currents under oblique waves.
The research provided a rare empirical test to the theoretical design concepts, and
potential supplements or refinements. To obtain the required beach protection, the
reef impact on the beach morphodynamic coupling including wave
transformation, nearshore hydrodynamics, and small/large scale beach state
response needs to be carefully assessed.

text: Oceanographic and morphodynamic monitoring of a multi-purpose reef at Mount Maunganui, New Zealand The innovative concept of an offshore submerged multi-purpose reef combining a
coastal protection function with recreational benefits including improved surfing,
diving, or fishing conditions provides an appealing solution for the management
of beaches. However, since the technology is relatively recent, there is still a lack
of empirical knowledge about its performance in the field. The present research
monitored the effect of the prototype  research  reef constructed at Mount
Maunganui in New Zealand on the local beach morphodynamics and
oceanographic conditions, being primarily concerned with implications on the
coastal protection function of the technology.
The beach morphodynamic response to the reef was investigated from a set of
already available high resolution bathymetric surveys imaging the foreshore and
surfzone morphology prior to, and throughout reef construction, and a new postconstruction
survey collected as a part of this research. The reef implementation
was found to disturb the pre-existing beach state functioning including the
onshore/offshore migration of the underlying long shore bar, rather than cause a
persistent salient response. A possible additional beach width of ~ 20 m,
extending ~ 150 m alongshore was identified in the lee of the reef from shoreline
analysis, but the pattern was transient throughout the monitoring period since it
was superimposed on comparatively large pre-existing fluctuations. In addition,
the reef structure provided a control point on the offshore morphology able to trap
sediment updrift and erode sediment downdrift.
Both field measurements and numerical modelling of waves and currents were
used to monitor the effect of the reef on the oceanographic conditions. Wave
propagation over the reef without breaking (H less than 0.5 m) resulted in transmitted
heights larger than incident by up to a factor of 2. When the reef triggered
breaking, transmitted heights were reduced by up to ~40 %. A concurrent process
was the shift of the wave energy spectra towards higher frequencies landward of
the reef that resulted in reduced transmitted wave periods. Wave modelling
showed that the wave shadowing was associated with significant wave rotation
around the reef that induced two zones of divergent wave angles near the
shoreline in the lee of the reef. The hydrodynamic response to the wave energy
dissipation was the development of stronger onshore directed currents landward of
the reef. Hydrodynamic modelling indicated that the reef-induced flow forced a
cellular circulation in the lee side under shore normal waves, and an onshore
deviation of the ambient (unidirectional) long-shore currents under oblique waves.
The research provided a rare empirical test to the theoretical design concepts, and
potential supplements or refinements. To obtain the required beach protection, the
reef impact on the beach morphodynamic coupling including wave
transformation, nearshore hydrodynamics, and small/large scale beach state
response needs to be carefully assessed.

year: 2010

title: Comparative fish abundance in the shallow Waikato lakes Whangape and Hakanoa

authors: Hicks, Brendan J.

abstract: The Waikato-Tainui College for Research and Development contracted the University of Waikato to conduct boat electrofishing estimates of the fish abundance in lakes Whangape and Hakanoa; both are shallow, riverine lakes in the lower Waikato River floodplain and are about 2,000 years old. Lake Whangape (latitude 37.46853°S, longitude 175.05120°W) is a large (1,450 ha), shallow (maximum depth 2.7 m) lake to the west of the Waikato River; Lake Hakanoa (latitude 37.55258°S, longitude 175.16859°W) is a 52-ha lake in suburban Huntly with a maximum depth of 2.5 m.
We fished 10 sites for 10 mins in both lakes Whangape and Lake Hakanoa; sites fished were 253-609 m long (1,012-2,436 m² in area) in Lake Whangape and 125-276 m long (500-1,104 m² in area) in Lake Hakanoa.
No submerged aquatic macrophytes were seen in either lake. Fishing was conducted close to the water's edge in Lake Hakanoa, but the shallow margins in Lake Whangape restricted fishing at most sites to 30-70 m from the shoreline. The shoreline was much more accessible in Lake Hakanoa, and was dominated by raupo (Typha orientalis) with willows (Salix spp.) in places. Submerged tree trunks and logs in Lake Hakanoa made navigation difficult in parts of the lake margins.
We caught a total of 118 fish in Lake Whangape, where shortfin eels (Anguilla australis) were the most abundant fish, and 594 fish in Lake Hakanoa, where gambusia (Gambusia affinis) the most abundant species. In Lake Whangape, shortfin eels comprised the greatest total biomass (12.4 kg), with koi carp (Cyprinus carpio) almost equally abundant (11.4 kg). In Lake Hakanoa, koi carp were most abundant (74.4 kg), followed by shortfin eels (22.1 kg).
Fish were unevenly spread among sites in Lake Whangape and koi carp were relatively sparsely among sites. In Lake Hakanoa, in contrast, fish were more evenly spread among sites, but with higher concentrations of catfish (Ameiurus nebulosus) and goldfish (Carassius auratus) at a few sites. Biomass of fish caught in each of the ten 10-min fishing shots reflected the numerical distributions, with some wide variations between sites. Fish densities were generally lower in Lake Whangape than in Lake Hakanoa; however, common smelt (Retropinna retropinna) and grey mullet (Mugil cephalus) occurred in Whangape but not in Hakanoa. Areal fish biomass was dominated by shortfin eels and koi carp in Lake Whangape, but koi carp dominated the fish biomass in Lake Hakanoa, despite the smaller number of carp than eels. This was because of the large mean weight of koi carp (about 1,000 g) compared to the smaller shortfin eels (mean weight about 200 g in both lakes).

text: Comparative fish abundance in the shallow Waikato lakes Whangape and Hakanoa The Waikato-Tainui College for Research and Development contracted the University of Waikato to conduct boat electrofishing estimates of the fish abundance in lakes Whangape and Hakanoa; both are shallow, riverine lakes in the lower Waikato River floodplain and are about 2,000 years old. Lake Whangape (latitude 37.46853°S, longitude 175.05120°W) is a large (1,450 ha), shallow (maximum depth 2.7 m) lake to the west of the Waikato River; Lake Hakanoa (latitude 37.55258°S, longitude 175.16859°W) is a 52-ha lake in suburban Huntly with a maximum depth of 2.5 m.
We fished 10 sites for 10 mins in both lakes Whangape and Lake Hakanoa; sites fished were 253-609 m long (1,012-2,436 m² in area) in Lake Whangape and 125-276 m long (500-1,104 m² in area) in Lake Hakanoa.
No submerged aquatic macrophytes were seen in either lake. Fishing was conducted close to the water's edge in Lake Hakanoa, but the shallow margins in Lake Whangape restricted fishing at most sites to 30-70 m from the shoreline. The shoreline was much more accessible in Lake Hakanoa, and was dominated by raupo (Typha orientalis) with willows (Salix spp.) in places. Submerged tree trunks and logs in Lake Hakanoa made navigation difficult in parts of the lake margins.
We caught a total of 118 fish in Lake Whangape, where shortfin eels (Anguilla australis) were the most abundant fish, and 594 fish in Lake Hakanoa, where gambusia (Gambusia affinis) the most abundant species. In Lake Whangape, shortfin eels comprised the greatest total biomass (12.4 kg), with koi carp (Cyprinus carpio) almost equally abundant (11.4 kg). In Lake Hakanoa, koi carp were most abundant (74.4 kg), followed by shortfin eels (22.1 kg).
Fish were unevenly spread among sites in Lake Whangape and koi carp were relatively sparsely among sites. In Lake Hakanoa, in contrast, fish were more evenly spread among sites, but with higher concentrations of catfish (Ameiurus nebulosus) and goldfish (Carassius auratus) at a few sites. Biomass of fish caught in each of the ten 10-min fishing shots reflected the numerical distributions, with some wide variations between sites. Fish densities were generally lower in Lake Whangape than in Lake Hakanoa; however, common smelt (Retropinna retropinna) and grey mullet (Mugil cephalus) occurred in Whangape but not in Hakanoa. Areal fish biomass was dominated by shortfin eels and koi carp in Lake Whangape, but koi carp dominated the fish biomass in Lake Hakanoa, despite the smaller number of carp than eels. This was because of the large mean weight of koi carp (about 1,000 g) compared to the smaller shortfin eels (mean weight about 200 g in both lakes).

year: 2016